Pumped heat energy storage system with thermal plant integration

ABSTRACT

The present disclosure provides pumped heat energy storage systems that can be used to store and/or extract electrical energy. A pumped heat energy storage system of the present disclosure can store energy by operating as a heat pump, whereby net work input can be used to transfer heat from the cold side to the hot side. A working fluid of the system is capable of efficient heat exchange with heat storage fluids on a hot side of the system and on a cold side of the system. Such pumped energy storage systems can be beneficially integrated with thermal plants to provided heat transfer to and/or from the thermal plants.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application No. 63/064,682, filed Aug. 12, 2020. The disclosureset forth in the referenced application is incorporated herein byreference in its entirety.

BACKGROUND

In a heat engine or heat pump, a heat exchanger may be employed totransfer heat between a thermal storage material and a working fluid foruse with turbomachinery. The heat engine may be reversible, e.g., it mayalso be a heat pump, and the working fluid and heat exchanger may beused to transfer heat or cold to thermal storage media.

SUMMARY

A Pumped Heat Electric Storage (“PHES”) system may include at least aworking fluid circulated through a closed cycle fluid path including atleast two heat exchangers, at least one turbine, and at least onecompressor. In some systems, one or more recuperative heat exchangersmay also be included. One or more thermal reservoirs may hold one ormore thermal fluids which may be sent through the heat exchangers,providing thermal energy to, and/or extracting thermal energy from, theworking fluid. One or more motor/generators may be used to obtain workfrom the thermal energy in the system, preferably by generatingelectricity from mechanical energy received from the turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates operating principles of a pumped heatelectric storage system.

FIG. 2 is a top-level schematic diagram of a PHES system with a dualpowertrain, according to an example embodiment.

FIG. 3 is a schematic fluid path diagram of a working fluid loopsubsystem in a PHES system, according to an example embodiment.

FIGS. 3A-3D are schematic fluid path diagrams of a generation powertrainsystem and associated valves, according to example embodiments.

FIGS. 3E-3H are schematic fluid path diagrams of a charge powertrainsystem and associated valves, according to example embodiments.

FIGS. 3I-3J are schematic fluid path diagrams of an ambient coolersystem and associated valves, according to example embodiments.

FIGS. 3K-3L are schematic fluid path diagrams of an ambient coolersystem and associated valves, according to example embodiments.

FIG. 3M is a schematic fluid path diagram of an inventory controlsystem, according to an example embodiment.

FIG. 3N is a schematic fluid path diagram of circulatory flow pathsduring charge mode.

FIG. 3O is a schematic fluid path diagram of circulatory flow pathsduring generation mode.

FIG. 4 is a schematic fluid path diagram of a hot-side thermal storagesystem, according to an example embodiment.

FIG. 5 is a schematic fluid path diagram of a cold-side thermal storagesystem, according to an example embodiment.

FIG. 6A is a schematic fluid path diagram of a main heat exchangersystem, according to an example embodiment.

FIG. 6B is a schematic fluid path diagram of a main heat exchangersystem, according to an example embodiment.

FIG. 7 is a schematic diagram of a generation powertrain (“GPT”) system,according to an example embodiment.

FIG. 8 is a schematic diagram of a charge powertrain (“CPT”) system,according to an example embodiment.

FIG. 9 is a schematic electrical diagram of a power interface, accordingto an example embodiment.

FIG. 10 illustrates primary modes of operation of a PHES system,according to an example embodiment.

FIG. 11 is a state diagram illustrating operating states of a PHESsystem, according to an example embodiment.

FIG. 12 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 13 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 14 is a state diagram illustrating generation powertrain states ofa PHES system, according to an example embodiment.

FIG. 15 is a state diagram illustrating charge powertrain states of aPHES system, according to an example embodiment.

FIG. 16 is a state diagram illustrating generation powertrain valvestates of a PHES system, according to an example embodiment.

FIG. 17 is a state diagram illustrating charge powertrain valve statesof a PHES system, according to an example embodiment.

FIG. 18 is a state diagram illustrating ambient cooler states of a PHESsystem, according to an example embodiment.

FIG. 19 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 20 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 21 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 22 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 23 is a state diagram illustrating select operating andtransitional states of a PHES system, according to an exampleembodiment.

FIG. 24 is a simplified block diagram illustrating components of a PHESsystem, according to an example embodiment.

FIG. 24A illustrates select controllers that can be implemented in aPHES system, according to an example embodiment.

FIG. 25 is a state diagram illustrating hot-side loop states of a PHESsystem, according to an example embodiment.

FIG. 26 is a state diagram illustrating cold-side loop states of a PHESsystem, according to an example embodiment.

FIG. 27 is a top-level schematic diagram of a PHES system with a sharedpowertrain, according to an example embodiment.

FIG. 28 is a schematic fluid path diagram of a working fluid loopsubsystem in a PHES system with a shared powertrain, according to anexample embodiment.

FIG. 28A is a schematic fluid path diagram of circulatory flow pathsduring charge mode.

FIG. 28B is a schematic fluid path diagram of circulatory flow pathsduring generation mode.

FIG. 29 is a top-level schematic diagram of a PHES system with areversible powertrain, according to an example embodiment.

FIG. 30 is a schematic fluid path diagram of a working fluid loopsubsystem in a PHES system with a reversible powertrain, according to anexample embodiment.

FIG. 30A is a schematic fluid path diagram of circulatory flow pathsduring charge mode.

FIG. 30B is a schematic fluid path diagram of circulatory flow pathsduring generation mode.

FIG. 31A is a schematic fluid path diagram of circulatory flow paths ofa main heat exchanger system during charge mode

FIG. 31B is a schematic fluid path diagram of circulatory flow paths ofa main heat exchanger system during generation mode

FIG. 32A is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 32B is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 32C is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 32D is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 32E is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 32F is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 33A is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 33B is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 33C is a schematic diagram of a power transmission system,according to an example embodiment.

FIG. 34A is a schematic diagram of modular turbomachinery with sharedpowertrains, according to an example embodiment.

FIG. 34B is a schematic diagram of modular turbomachinery with sharedpowertrains, according to an example embodiment.

FIG. 34C is a schematic diagram of modular turbomachinery with a sharedpowertrain, according to an example embodiment.

FIG. 35A is a schematic diagram of modular turbomachinery withreversible powertrains, according to an example embodiment.

FIG. 35B is a schematic diagram of modular turbomachinery withreversible powertrain, according to an example embodiment.

FIG. 35C is a schematic diagram of modular turbomachinery with areversible powertrain, according to an example embodiment.

FIG. 36 is a top-level schematic diagram of a PHES system in charge modeintegrated with a power generation plant, according to an exampleembodiment.

FIG. 36A is a schematic diagram of a portion of a powertrain systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 37A is a schematic diagram of a hot-side thermal storage systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 37B is a schematic diagram of cold-side thermal storage systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 38 is a top-level schematic diagram of a PHES system in generationmode integrated with a power generation plant, according to an exampleembodiment.

FIG. 38A is a schematic diagram of a portion of a powertrain systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 39 is a schematic diagram of cogeneration control of a PHES systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 40 is a simplified block diagram illustrating components of acogeneration system, according to an example embodiment.

FIG. 41 is a schematic diagram of district heating with a PHES systemintegrated with a power generation plant, according to an exampleembodiment.

FIG. 42 is a top-level schematic diagram of a PHES system in charge modeintegrated with a power generation plant, according to an exampleembodiment.

FIG. 43 is a top-level schematic diagram of a PHES system in generationmode integrated with a power generation plant, according to an exampleembodiment.

FIG. 44 is a top-level schematic diagram of a steam plant integratedwith a PHES system, according to an example embodiment.

FIG. 45 is a top-level schematic diagram of a steam plant integratedwith a PHES system, according to an example embodiment.

DETAILED DESCRIPTION I. Overview

The Pumped Heat Electric Storage (“PHES”) systems, modes of operations,and states disclosed herein, as illustrated via multiple embodiments,are grid-scale energy storage systems that provide dispatchable powergeneration and power absorption. The terms grid and electrical grid areused interchangeably herein, and may refer to, for example, regional,national, and/or transnational electrical grids where an interconnectednetwork delivers electricity from power generation plants and energystorage systems to consumers or other electrical grids. Advantageously,the PHES systems may provide increased grid stability and resilience.Additionally or alternatively, embodiments disclosed herein can achievevery fast dispatch response times, with spinning reserve capabilitiescomparable to natural gas peaker and cyclic units, but without thefossil fuel consumption. The PHES systems disclosed herein, utilizingthermal storage media also disclosed herein, may advantageously providea safe, non-toxic and geography-independent energy (e.g., electricity)storage alternative.

The PHES systems function as thermodynamic cycle power generation and/orenergy storage systems. Embodiments of the PHES systems may work asBrayton cycle systems. Alternatively or additionally, embodiments of thePHES systems may work as reversible Brayton cycle systems. Preferably,the PHES systems may operate as closed working-fluid loop systems. ThePHES systems may use one or more generator and/or motor systems, whichconnect to one or more turbines and/or compressors which act on aworking fluid (e.g., air) circulating in the system.

The PHES systems may have a hot side and a cold side. Each side mayinclude one or more heat exchanger systems coupled to one or morethermal reservoirs. The PHES systems may employ liquid thermal storagemedium on both or either the hot side and/or the cold side. The liquidthermal storage media preferably include liquids that are stable at hightemperatures, such as molten nitrate salt or solar salt, and/or liquidsthat are stable at low temperatures, such as methanol/water coolantmixtures, glycols, and/or alkanes such as hexane. In one embodiment,cold-side and hot-side thermal reservoirs may include tanks of liquidthermal storage media, such as, but not limited to, methanol/watercoolant and molten salt, respectively.

During a charge cycle (i.e., charge mode), the PHES systems act as aheat pump, converting electrical energy from an electrical grid or othersource to thermal energy that is stored in thermal reservoirs. Theheat-pumping action may be done via motor-driven turbomachinery (e.g., acompressor system and a turbine system) in a closed-loop Brayton cycleusing a working fluid (e.g., air).

During a generation cycle (i.e., generation mode), the PHES systems actas a heat engine, converting stored thermal energy from the thermalreservoirs to electrical energy that can be dispatched back to the gridor another load. The working fluid loop during generation may be aclosed-loop Brayton cycle, may use the same working fluid as the chargecycle, may use the same or different heat exchangers as the chargecycle, and may use the same turbomachinery as the charge cycle or mayuse different turbomachinery than the charge cycle. The generationturbine system may drive one or more generators that are gridsynchronous.

Embodiments of the disclosed PHES systems enable fast cycling from fullcharge to full discharge.

Embodiments of the PHES systems also enable fast mode switching, suchthat the PHES system can switch modes from full load (i.e., charge) tofull generation in a very short duration. This is particularly usefulfor providing spinning reserve type capabilities to address energyshifting needs related to high penetration of solar (e.g., photovoltaic)energy generation on an electrical grid or grid segment. During rampperiods when solar generation is coming online or going offline, theability of the PHES systems to quickly change from full load to fullgeneration is critical for helping to address slope of the solar “duckcurve” that reflects a timing imbalance between peak demand andrenewable energy production.

Embodiments of the PHES systems also enable partial turndown. Variouspower generation applications (e.g. wind farms, natural gas peaker powerplants) benefit from the ability for generation and load assets such asthe PHES systems to ramp power up and down from full power based on adispatching signal.

FIG. 1 schematically illustrates operating principles of the PHESsystems. Electricity may be stored in the form of thermal energy of twothermal storage media at different temperatures (e.g., thermal energyreservoirs comprising thermal storage media such as heat storage fluids)by using one or more heat pump and heat engine systems. In a charging(heat pump) mode, work may be consumed by the PHES system fortransferring heat from a cold thermal medium to a hot thermal medium,thus lowering the temperature of the cold thermal medium and increasingthe temperature of the hot thermal medium. In a generation (heat engineor discharging) mode, work may be produced by the PHES systems bytransferring heat from the hot thermal medium to the cold thermalmedium, thus lowering the temperature (i.e., sensible energy) of the hotthermal medium and increasing the temperature of the cold thermalmedium. The PHES systems may be configured to ensure that the workproduced by the system during generation is a favorable fraction of theenergy consumed during charge. Excess heat from inefficiency may bedumped to ambient or an external heat sink. The PHES systems areconfigured to achieve high roundtrip efficiency, defined herein as thework produced by the system during generation divided by the workconsumed by the system during charge. Further, the design of the PHESsystems permits high roundtrip efficiency using components of a desired(e.g., acceptably low) cost.

The PHES systems may include a working fluid to and from which heat istransferred while undergoing a thermodynamic cycle. The PHES systemsoperating in a closed cycle allows, for example, a broad selection ofworking fluids, operation at elevated hot side pressures, operation atlower cold side temperatures, improved efficiency, and reduced risk ofcompressor and turbine damage. One or more aspects of the disclosuredescribed in relation to the PHES systems having working fluidsundergoing closed thermodynamic cycles may also be applied to the PHESsystems having working fluids undergoing open or semi-open thermodynamiccycles.

The working fluid may undergo a thermodynamic cycle operating at one,two, or more pressure levels. For example, the working fluid may operatein a closed cycle between a low-pressure limit on a cold side of thesystem and a high-pressure limit on a hot side of the system. In someimplementations, a low-pressure limit of about 10 atmospheres (atm) orgreater can be used. In some instances, the low pressure limit may be atleast about 1 atm, at least about 2 atm, at least about 5 atm, at leastabout 10 atm, at least about 15 atm, at least about 20 atm, at leastabout 30 atm, at least about 40 atm, at least about 60 atm, at leastabout 80 atm, at least about 100 atm, at least about 120 atm, at leastabout 160 atm, or at least about 200 atm, 500 atm, 1000 atm, or more. Insome instances, a sub-atmospheric low-pressure limit may be used. Forexample, the low-pressure limit may be less than about 0.1 atm, lessthan about 0.2 atm, less than about 0.5 atm, or less than about 1 atm.In some instances, the low-pressure limit may be about 1 atmosphere(atm). In the case of a working fluid operating in an open cycle, thelow-pressure limit may be about 1 atm or equal to ambient pressure.

Working fluids used in embodiments of the PHES systems may include air,argon, other noble gases, carbon dioxide, hydrogen, oxygen, or anycombination thereof, and/or other fluids in gaseous state throughout theworking fluid loop. In some implementations, a gas with a high specificheat ratio may be used to achieve higher cycle efficiency than a gaswith a low specific heat ratio. For example, argon (e.g., specific heatratio of about 1.66) may be used rather than air (e.g., specific heatratio of about 1.4). In some cases, the working fluid may be a blend ofone, two, three, or more fluids. In one example, helium (having a highthermal conductivity and a high specific heat) may be added to theworking fluid (e.g., argon) to improve heat transfer rates in heatexchangers.

The PHES systems may utilize thermal storage media, such as one or moreheat storage fluids. Alternatively or additionally, the thermal storagemedia may be solids or gasses, or a combination of liquids, solids,and/or gasses. The PHES systems may utilize a thermal storage medium ona hot side of the PHES system (“HTS medium”) and a thermal storagemedium on a cold side of the system (“CTS medium”). Preferably, thethermal storage media have high heat capacities per unit volume (e.g.,heat capacities above about 1400 Joule (kilogram Kelvin)-1) and highthermal conductivities (e.g., thermal conductivities above about 0.7Watt (meter Kelvin)-1). In some implementations, several differentthermal storage media on either the hot side or the cold side, or boththe hot side and the cold side, may be used.

The operating temperatures and pressures of the HTS medium may beentirely in the liquid range of the HTS medium, and the operatingtemperatures and pressures of the CTS medium may be entirely in theliquid range of the CTS medium. In some examples, liquids may enable amore rapid exchange of large amounts of heat than solids or gases. Thus,in some cases, liquid HTS and CTS media may advantageously be used.

In some implementations, the HTS medium may be a molten salt or amixture of molten salts. A salt or salt mixture that is liquid over theoperating temperature range of the HTS medium may be employed. Moltensalts can provide numerous advantages as thermal storage media, such aslow vapor pressure, lack of toxicity, chemical stability, low reactivitywith typical steels (e.g., melting point below the creep temperature ofsteels, low corrosiveness, low capacity to dissolve iron and nickel),and low cost. In one example, the HTS medium is a mixture of sodiumnitrate and potassium nitrate. In another example, the HTS medium is aeutectic mixture of sodium nitrate and potassium nitrate. In anotherexample, the HTS medium is a mixture of sodium nitrate and potassiumnitrate having a lowered melting point than the individual constituents,an increased boiling point than the individual constituents, or acombination thereof. Other examples of HTS media include potassiumnitrate, calcium nitrate, sodium nitrate, sodium nitrite, lithiumnitrate, mineral oil, or any combination thereof. Further examplesinclude any gaseous (including compressed gases), liquid or solid media(e.g., powdered solids) having suitable (e.g., high) thermal storagecapacities and/or are capable of achieving suitable (e.g., high) heattransfer rates with the working fluid. For example, a mix of 60% sodiumnitrate and 40% potassium nitrate (also referred to as a solar salt) canhave a heat capacity of approximately 1500 Joule (Kelvin mole)-1 and athermal conductivity of approximately 0.75 Watt (meter Kelvin)-1 withina temperature range of interest. Advantageously, the HTS medium may beoperated in a temperature range that is compatible with structuralsteels used in unit components of the PHES system.

In some cases, liquid water at temperatures of about 0° C. to 100° C.(about 273 K-373 K) and a pressure of about 1 atm may be used as the CTSmedium. Due to a possible explosion hazard associated with the presenceof steam at or near the boiling point of water, the operatingtemperature can be kept below 100° C. while maintaining an operatingpressure of 1 atm (i.e., no pressurization). In some cases, thetemperature operating range of the CTS medium may be extended (e.g., to−30° C. to 100° C. at 1 atm) by using a mixture of water and one or moreantifreeze compounds (e.g., ethylene glycol, propylene glycol, orglycerol), or a water/alcohol mixture such as water and methanol.

Improved efficiency may be achieved by increasing the temperaturedifference at which the PHES system operates, for example, by using aCTS medium capable of operating at lower temperatures. In some examples,the CTS medium may comprise hydrocarbons, such as, for example, alkanes(e.g., hexane or heptane), alkenes, alkynes, aldehydes, ketones,carboxylic acids (e.g., HCOOH), ethers, cycloalkanes, aromatichydrocarbons, alcohols (e.g., butanol), other type(s) of hydrocarbonmolecules, or any combinations thereof. In some examples, cryogenicliquids having boiling points below about −150° C. or about −180° C. maybe used as CTS medium (e.g., propane, butane, pentane, nitrogen, helium,neon, argon, krypton, air, hydrogen, methane, or liquefied natural gas,or combinations thereof). In some implementations, choice of CTS mediummay be limited by the choice of working fluid. For example, when agaseous working fluid is used, a liquid CTS medium having a liquidtemperature range at least partially or substantially above the boilingpoint of the working fluid may be required.

In some cases, the operating temperature range of CTS and/or HTS mediacan be changed by pressurizing (i.e., raising the pressure) orevacuating (i.e., lowering the pressure) the thermal media fluid pathsand storage tanks, and thus changing the temperature at which thestorage media undergo phase transitions.

The HTS medium and/or CTS medium may be in a liquid state over all, orover at least a portion, of the operating temperature range of therespective side of a PHES system. The HTS medium and/or CTS medium maybe heated, cooled or maintained to achieve a suitable operatingtemperature prior to, during or after various modes of operation of aPHES system.

The thermal reservoirs of the PHES systems may cycle between charged anddischarged modes, in conjunction with, or separate from, the charge andgeneration cycles of the overall PHES system embodiment. In someexamples, the thermal reservoirs of the PHES systems may be fullycharged, partially charged or partially discharged, or fully discharged.In some cases, cold-side thermal reservoir(s) may be charged (also“recharged” herein) independently from hot-side thermal reservoir(s).Further, in some implementations, charging (or some portion thereof) ofthermal reservoirs and discharging (or some portion thereof) of thermalreservoirs can occur simultaneously. For example, a first portion of ahot-side thermal reservoir may be recharged while a second portion ofthe hot-side thermal reservoir together with a cold-side thermalreservoir are being discharged.

Embodiments of the PHES systems may be capable of storing energy for agiven amount of time. In some cases, a given amount of energy may bestored for at least about 1 second, at least about 30 seconds, at leastabout 1 minute, at least about 5 minutes, at least about 30 minutes, atleast about 1 hour, at least about 2 hours, at least about 3 hours, atleast about 4 hours, at least about 5 hours, at least about 6 hours, atleast about 7 hours, at least about 8 hours, at least about 9 hours, atleast about 10 hours, at least about 12 hours at least about 14 hours,at least about 16 hours, at least about 18 hours, at least about 20hours, at least about 22 hours, at least about 24 hours (1 day), atleast about 2 days, at least about 4 days, at least about 6 days, atleast about 8 days, at least about 10 days, 20 days, 30 days, 60 days,100 days, 1 year or more.

Embodiments of the PHES systems may be capable of storing/receivinginput of, and/or extracting/providing output of, a substantially largeamount of energy for use with power generation systems (e.g.,intermittent power generation systems such as wind power or solarpower), power distribution systems (e.g. electrical grid), and/or otherloads or uses in grid-scale or stand-alone settings. During a chargemode of the PHES systems, electric power received from an external powersource (e.g., a wind power system, a solar photovoltaic power system, anelectrical grid, etc.) can be used to operate the PHES systems in theheat pump mode (i.e., transferring heat from a low temperature reservoirto a high temperature reservoir, thus storing energy). During ageneration mode of the PHES systems, the system can supply electricpower to an external power system or load (e.g., one or more electricalgrids connected to one or more loads, a load, such as a factory or apower-intensive process, etc.) by operating in the heat engine mode(i.e., transferring heat from a high temperature reservoir to a lowtemperature reservoir, thus extracting energy). As described elsewhereherein, during charge and/or generation, the system may receive orreject thermal power, including, but not limited to electromagneticpower (e.g., solar radiation) and thermal power (e.g., sensible energyfrom a medium heated by solar radiation, heat of combustion etc.).

In some implementations, the PHES systems are grid-synchronous.Synchronization can be achieved by matching speed and frequency ofmotors and/or generators and/or turbomachinery of a system with thefrequency of one or more grid networks with which the PHES systemsexchange power. For example, a compressor and a turbine can rotate at agiven, fixed speed (e.g., 3600 revolutions per minute (rpm)) that is amultiple of North American grid frequency (e.g., 60 hertz (Hz)). In somecases, such a configuration may eliminate the need for additional powerelectronics. In some implementations, the turbomachinery and/or themotors and/or generators are not grid synchronous. In such cases,frequency matching can be accomplished through the use of powerelectronics. In some implementations, the turbomachinery and/or themotors and/or generators are not directly grid synchronous but can bematched through the use of gears and/or a mechanical gearbox. Asdescribed in greater detail elsewhere herein, the PHES systems may alsobe power and/or load rampable. Such capabilities may enable thesegrid-scale energy storage systems to operate as peaking power plantsand/or as a load following power plants. In some cases, the PHES systemsof the disclosure may be capable of operating as base load power plants.

Embodiments of the PHES systems can have a given power capacity. In somecases, power capacity during charge may differ from power capacityduring discharge. For example, embodiments of the PHES system can have acharge and/or discharge power capacity of less than about 1 megawatt(MW), at least about 1 megawatt, at least about 2 MW, at least about 3MW, at least about 4 MW, at least about 5 MW, at least about 6 MW, atleast about 7 MW, at least about 8 MW, at least about 9 MW, at leastabout 10 MW, at least about 20 MW, at least about 30 MW, at least about40 MW, at least about 50 MW, at least about 75 MW, at least about 100MW, at least about 200 MW, at least about 500 MW, at least about 1gigawatt (GW), at least about 2 GW, at least about 5 GW, at least about10 GW, at least about 20 GW, at least about 30 GW, at least about 40 GW,at least about 50 GW, at least about 75 GW, at least about 100 GW, ormore.

Embodiments of the PHES systems can have a given energy storagecapacity. In one example, a PHES system embodiment may be configured asa 100 MW unit operating for 10-hour cycles. In another example, a PHESsystem embodiment may be configured as a 1 GW plant operating for12-hour cycles. In some instances, the energy storage capacity can beless than about 1 megawatt hour (MWh), at least about 1 megawatt hour,at least about 10 MWh, at least about 100 MWh, at least about 1 gigawatthour (GWh), at least about 5 GWh, at least about 10 GWh, at least about20 GWh, at least 50 GWh, at least about 100 GWh, at least about 200 GWh,at least about 500 GWh, at least about 700 GWh, at least about 1000 GWh,or more.

In some cases, a given power capacity may be achieved with a given size,configuration and/or operating conditions of the heat engine/heat pumpcycle. For example, size of turbomachinery and/or heat exchangers,number of turbomachinery and/or heat exchangers, or other systemcomponents, may correspond to a given power capacity. In someembodiments, the rate at which a PHES system reaches capacity may varybetween cycles depending on configuration and/or operating conditions ofthe heat engine/heat pump cycle. For example, size of turbomachineryand/or number of turbomachinery may vary between cycles.

In some implementations, a given energy storage capacity may be achievedwith a given size and/or number of hot-side thermal reservoir(s) and/orcold-side thermal reservoir(s). For example, the heat engine/heat pumpcycle can operate at a given power capacity for a given amount of timeset by the heat storage capacity of the thermal reservoir(s). The numberand/or heat storage capacity of the hot-side thermal reservoir(s) may bedifferent from the number and/or heat storage capacity of the cold-sidethermal reservoir(s). The number of thermal reservoir(s) may depend onthe size of individual thermal reservoir(s).

Embodiments of the PHES systems may include any suitable number ofcold-side and/or hot-side thermal storage units (e.g., CTS medium and/orHTS medium storage tanks, respectively), such as, but not limited to, atleast about 1 (divided into two sections), at least about 2, at leastabout 4, at least about 10, at least about 50, at least about 100, andthe like. In some examples, embodiments of the PHES system include 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or morethermal storage units (e.g., CTS medium and/or HTS medium storagetanks).

A steam plant may operate in conjunction with one or more cycles of aPHES system, for example by utilizing thermal energy stored by the PHESsystem during a charge cycle. A PHES system integrated with a steamplant may take multiple forms. For example, an integrated PHES systemmay be a complete PHES system as described herein, or an integrated PHESmay not include components necessary for operating in a generationcycle. The steam plant may generate electricity for distribution to, forexample, an electrical grid or load. Additionally, a heater may be usedto further increase the heat stored in the PHES system, thus increasingthe amount of stored thermal energy available to the steam plant.Embodiments of an integrated steam plant and PHES system may operate invarious combinations of modes, including but not limited to: the PHESsystem operating in a charge mode while the steam plant is idle; thePHES system in an idle mode, such as slow-rolling, hot standby, orcold-dry standby while the steam plant is in a generation mode; the PHESsystem operating in a charge mode and the steam plant operating in ageneration mode; and/or, the PHES system in a generation mode and thesteam plant in a generation mode.

While various embodiments of the invention are shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed. It shall be understood that different aspects of the inventioncan be appreciated individually, collectively, or in combination witheach other.

Descriptions and illustrations provided herein in the context of aparticular PHES system embodiment (e.g., PHES system 1000), includingcomponents, fluids, controls, functions, operations, capabilities,systems, subsystems, configurations, arrangements, modes, states,benefits, and advantages should be considered applicable to other PHESsystem embodiments (e.g., PHES systems 1003 and 1005), and vice-versa.

It is to be understood that the terminology used herein is used for thepurpose of describing specific embodiments, and is not intended to limitthe scope of the present invention. It should be noted that as usedherein, the singular forms of “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. In addition,unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

While preferable embodiments of the present invention are shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

The term “reversible,” as used herein, generally refers to a process oroperation that can be reversed. In some examples, in a reversibleprocess, the direction of flow of energy is reversible. As analternative, or in addition to, the general direction of operation of areversible process (e.g., the direction of fluid flow) can be reversed,such as, e.g., from clockwise to counterclockwise, and vice versa.

The term “sequence,” as used herein, generally refers to elements (e.g.,unit operations) in order. Such order can refer to process order, suchas, for example, the order in which a fluid flows from one element toanother. In an example, a compressor, heat exchange unit, and turbine insequence includes the compressor upstream of the heat exchange unit, andthe heat exchange unit upstream of the turbine. In such a case, a fluidcan flow from the compressor to the heat exchange unit and from the heatexchange unit to the turbine. A fluid flowing through unit operations insequence can flow through the unit operations sequentially. A sequenceof elements can include one or more intervening elements. For example, asystem comprising a compressor, heat storage unit and turbine insequence can include an auxiliary tank between the compressor and theheat storage unit. A sequence of elements can be cyclical.

II. Illustrative PHES System—Dual Powertrain

FIG. 2 is a top-level schematic diagram of a PHES system 1000 with dualpowertrains, according to an example embodiment, in which PHES systemembodiments herein may be implemented. As a top-level schematic, theexample embodiment PHES system 1000 in FIG. 2 illustrates majorsubsystems and select components, but not all components. Additionalcomponents are further illustrated with respect to additional figuresdetailing various subsystems. Additionally or alternatively, in otherembodiments, additional components and/or subsystems may be included,and/or components and/or subsystems may not be included. FIG. 2 furtherillustrates select components and subsystems that work together in thePHES system 1000. FIG. 2 schematically shows how the select componentsand subsystems connect, how they are grouped into major subsystems, andselect interconnects between them.

In FIG. 2 and other figures, for example, FIGS. 27 and 29, connectionsbetween subsystems are illustrated as interconnects, such as fluidinterconnects 3, 4 and electrical interconnects 15, 21. Illustratedconnections between fluid interconnects, electrical interconnects,and/or components reflect fluid paths or power/signal paths, asappropriate. For example, fluid path 901 connects fluid interconnect 2and fluid interconnect 3, thereby allowing fluid flow between CHX system600 and AHX system 700, described in further detail below. As anotherexample, power/signal path 902 connects electrical interconnect 15 andelectrical interconnect 15A, which can carry power/signals between powerinterface 2002 and motor system 110. Junctions between illustrated pathsare shown as a solid dot. For example, fluid path 903 exiting the mainheat exchanger system 300A at fluid interconnect 7 joins the fluid path904 between fluid interconnect 17 and fluid interconnect 23 at junction905. Fluid paths may include components, connections, valves, and pipingbetween components, and each fluid path may, in practice, include asingle flow path (e.g., a single pipe) or multiple (e.g. parallel) flowpaths (e.g., multiple pipes) between components. Valves may interrupt ormake fluid connections between various fluid paths, as elsewhereillustrated, such as in FIGS. 3, 28, 30. Valves may be activelycontrollable through actuators or other known devices in response tocontrol signals, or may change state (e.g., open to close) in responseto a physical condition at the valve, such as an overpressure conditionat a pressure relief device. Further, valves may include variableposition valves (e.g., capable of partial flow such as in proportionalor servo valves) or switching valves (e.g., either open or closed). Ifan illustrated valve is on a fluid path that in practice includesmultiple flow paths (e.g., multiple pipes), then each flow path mayconnect to the single valve or there may be multiple valves connectingthe multiple flow paths. For power/signal paths, switches, breakers, orother devices may interrupt or make power/signal connections betweenvarious power/signal paths, such as in FIG. 9.

Major subsystems of PHES system 1000 include a charge powertrain system(“CPT system”) 100, a generation powertrain system (“GPT system”) 200, aworking fluid loop 300, a main heat exchanger system 300A, a hot-sidethermal storage system (“HTS system”) 501, a cold-side thermal storagesystem (“CTS system”) 601, and site integration systems 2000.

In FIG. 2, illustrated components in CPT system 100 include charge motorsystem 110, charge gearbox system 120, charge compressor system 130, andcharge turbine system 140. Depending on operational mode, state, andembodiment configuration, CPT system 100 may connect to other componentsand subsystems of PHES system 1000 through various interconnects,including electrical interconnect 15 and fluid interconnects 17, 18, 19,and 20. Additionally, CPT system 100 may include more or fewerinterconnects than shown in FIG. 2. The CPT system 100 takes electricalpower in at electrical interconnect 15 and converts the electricalenergy to working fluid flows through one or more of its fluidinterconnects.

In FIG. 2, illustrated components in GPT system 200 include generatorsystem 210, generation gearbox system 220, generation compressor system230, and generation turbine system 240. Depending on operational mode,state, and embodiment configuration, GPT system 200 may connect to othercomponents and subsystems of PHES system 1000 through variousinterconnects, including electrical interconnect 21 and fluidinterconnects 22, 23, 25, and 26. Additionally, GPT system 200 mayinclude more or fewer interconnects than shown in FIG. 2. GPT system 200outputs electrical power at electrical interconnect 21 by taking energyfrom the working fluid flows through one or more of fluid interconnects.In some operating conditions or states, GPT system 200 may also receivepower through one or more of electrical interconnects, such aselectrical interconnect 21.

In FIG. 2, working fluid loop 300 includes a main heat exchanger system300A, which includes recuperator heat exchanger (“RHX”) system 400,hot-side heat exchanger (“HHX”) system 500, cold-side heat exchanger(“CHX”) system 600, and ambient cooler (heat exchanger) (“AHX”) system700. Depending on operational mode, state, and embodiment configuration,components in the main heat exchanger system 300A may connect to othercomponents and subsystems of the PHES system 1000, and/or othercomponents within the main heat exchanger system 300A or the workingfluid loop 300, through various interconnects, including fluidinterconnects 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 28, and 29.

In FIG. 2, working fluid loop 300 further includes the charge compressorsystem 130, and charge turbine system 140 of the CPT system 100, and thegeneration compressor system 230, and generation turbine system 240 ofthe GPT system 200. Depending on operational mode, state, and embodimentconfiguration, components in the working fluid loop 300 may connect toother components and subsystems of the PHES system 1000, and/or othercomponents within the working fluid loop 300, through variousinterconnects, including fluid interconnects 17, 18, 19, 20, 22, 23, 25,and 26.

In the PHES system 1000, working fluid loop 300 may act as a closedfluid path through which the working fluid circulates and in whichdesired system pressures of the working fluid can be maintained. Theworking fluid loop 300 provides an interface for the working fluidbetween the turbomachinery (e.g., charge compressor system 130 andcharge turbine system 140, and/or generation compressor system 230 andgeneration turbine system 240) and the heat exchangers in the main heatexchanger system 300A. In a preferred embodiment, the working fluid isair. Example embodiments, and portions thereof, of working fluid loop300, are illustrated in FIGS. 3 and 3A-O.

The working fluid loop 300 includes a fluid path that, in someoperational modes and/or states of PHES system 1000, carrieshigh-temperature and high-pressure working fluid between chargecompressor system 130 and HHX system 500. In other operational modesand/or states a fluid path carries high-temperature and high-pressureworking fluid between HHX system 500 and generation turbine system 240.Other configurations are possible as well. These configurations arefurther detailed with respect to the mode of operation and statedescriptions herein and FIGS. 3 and 3A-O.

The working fluid loop 300 includes a fluid path that, in someoperational modes and/or states of PHES system 1000, carriesmedium-temperature and high-pressure working fluid between RHX system400 and charge turbine system 140. In other operational modes and/orstates, a fluid path carries medium-temperature and high-pressureworking fluid between generation compressor system 230 and RHX system400. Other configurations are possible as well. These configurations arefurther detailed with respect to the mode of operation and statedescriptions herein and FIGS. 3 and 3A-O.

The working fluid loop 300 includes a fluid path that, in someoperational modes and/or states of PHES system 1000, carrieslow-temperature and low-pressure working fluid between charge turbinesystem 140 and CHX system 600. In other operational modes and/or statesa fluid path carries low-temperature and low-pressure working fluidbetween CHX system 600 and generation compressor system 230. Otherconfigurations are possible as well. These configurations are furtherdetailed with respect to the mode of operation and state descriptionsherein and FIGS. 3 and 3A-O.

The working fluid loop 300 includes a fluid path that, in someoperational modes and/or states of PHES system 1000, carriesmedium-temperature and low-pressure working fluid between RHX system 400and charge compressor system 130. In other operational modes and/orstates, a fluid path carries medium-temperature and low-pressure workingfluid between generation turbine system 240 and RHX system 400. Otherconfigurations are possible as well. These configurations are furtherdetailed with respect to the mode of operation and state descriptionsherein and FIGS. 3 and 3A-O.

The main heat exchanger system 300A facilitates heat transfer betweenthe working fluid circulating through the working fluid loop 300, a CTSmedium circulating from/to the CTS system 601, an HTX medium circulatingfrom/to the HTS system 501, and the ambient environment or other heatsink via AHX system 700. The CTS medium circulates between a warm CTSsystem 691 and a cold CTS system 692 via the CHX system 600, and thatcirculation may be referred to as the “CTS loop” or “cold-side loop,” asfurther described, e.g., with respect to a CTS system 601 embodimentillustrated in FIG. 5. In a preferred embodiment, the CTS medium is acoolant fluid, such as a methanol and water mixture. The HTS mediumcirculates between a warm HTS system 591 and a hot HTS system 592 viathe HHX system 500, and that circulation may be referred to as the “HTSloop” or “hot-side loop,” as further described, e.g., with respect to anHTS system 601 embodiment illustrated in FIG. 4. In a preferredembodiment, the HTX medium is a molten salt.

In FIG. 2, illustrated components in CTS system 601 include arepresentation of a cold-side thermal reservoir, including warm CTSsystem 691 and cold CTS system 692. Depending on operational mode,state, and embodiment configuration, CTS system 601 may connect to othercomponents and subsystems of PHES system 1000 through variousinterconnects, including fluid interconnects 1 and 31. An exampleembodiment of CTS system 601, including pumps and supporting fluidpaths, valves, and other components is illustrated in FIG. 5.

In FIG. 2, illustrated components in HTS system 501 include arepresentation of a hot-side thermal reservoir, including warm HTSsystem 591 and hot HTS system 592. Depending on operational mode, state,and embodiment configuration, HTS system 501 may connect to othercomponents and subsystems of PHES system 1000 through variousinterconnects, including fluid interconnects 6 and 8. An exampleembodiment of HTS system 501, including pumps and supporting fluidpaths, valves, and other components is illustrated in FIG. 4.

Components in PHES system 1000, including but not limited to valves,fans, sensors, pumps, heaters, heat traces, breakers, VFDs, workingfluid compressors, etc., may each be connected to a power source and maybe independently controllable, either or both proportionally and/orswitchably, via one or more controllers and/or control systems.Additionally, each such component may include, or be communicativelyconnected via, a signal connection with another such component, through,for example, a wired, optical, or wireless connections. For example, asensor may transmit data regarding temperature of the working fluid at alocation in the working fluid loop; and, a control system may receivethat data and responsively send a signal to a valve to close a fluidpath. Data transmission and component control via signaling is known inthe art and not illustrated herein, except wherein a particulararrangement is new and/or particularly relevant to the disclosed PHESsystems, as with, for example, FIG. 9.

A. Charge Powertrain Subsystem

FIG. 8 is a schematic diagram of the charge powertrain system 100,according to an example embodiment. FIG. 8 provides additional detailconcerning CPT system 100 beyond that shown in the top-level schematicof FIG. 2. The CPT system 100 may be implemented in PHES systemsdisclosed herein, including the PHES system 1000 embodiment illustratedin FIG. 2. Other embodiments of a charge powertrain system operable inPHES systems disclosed herein are possible as well.

In FIG. 8, CPT system 100 includes a motor 110-1 as part of the chargemotor system 110 of FIG. 2, a gearbox 120-1 as part of the chargegearbox system 120 of FIG. 2, a compressor 130-1 as part of chargecompressor system 130, and a turbine 140-1 as part of charge turbinesystem 140. These components are connected via a drivetrain 150, suchthat the motor 110-1 is capable of driving the gearbox 120-1, thecompressor 130-1, and the turbine 140-1. Drivetrain 150 may include afixed connection between compressor 130-1 and turbine 140-1, and/or mayinclude one or more shafts, flexible couplings, clutches, and/orgearboxes between compressor 130-1 and turbine 140-1. CPT system 100further includes a turning motor 121-1 that is additionally capable ofdriving the compressor 130-1 and/or the turbine 140-1. Within CPT system100, gearbox 120-1 provides a speed conversion between the motor 110-1and turning motor 121-1 and the turbomachinery. In other embodiments ofa charge powertrain system, the gearbox 120-1 may act only on one of themotors 110-1 and 121-1. Alternatively or additionally, gearbox 120-1 mayact only on motor 110-1 and another gearbox (or no gearbox) may act onturning motor 121-1. In another embodiment, gearbox 120-1 may beomitted, therefore resulting in no speed conversion.

Turning motor 121-1 may be used for spinning CPT system 100turbomachinery at low speeds (e.g., “slow roll”), for example, to coolthe compressor 130-1 following a shutdown, and before bringing therotating equipment to rest. The turning motor 121-1 may be mounted tothe gearbox 120-1 or the drivetrain 150 or the motor 110-1, orelsewhere, and preferably rotates the turbomachinery at a very low RPMcompared to the motor 110-1. The turning motor 121-1 is fitted with anoverrunning clutch 121-2 that disengages when the drivetrain 150 side ofthe clutch is operating at higher speeds than the turning motor 121-1.This results in the turning motor 121-2 engaging with the drivetrain 150when the slowing drivetrain 150 reaches the speed of the turning motor121-1. The turning motor 121-1 will then maintain the slow roll speed.

CPT system 100 can receive power into the subsystem (via, e.g.,electrical interconnect 15) and supply power to the motor system 110(e.g., motor 110-1) and/or the turning motor 121-1. Depending onoperational mode, state, and embodiment configuration, and as furtherillustrated in FIG. 2, CPT system 100 may receive power via a powerinterface 2002 and from the generator system 210 and/or an externalsource such as an electrical grid or local external generation source(e.g., power plant, renewable energy source, etc.) via interconnect 27.

Depending on operational mode and state, compressor 130-1 may raise thepressure of working fluid flowing through the compressor 130-1 by usingrotational energy transmitted through the drivetrain 150. For example,during a charging mode (e.g., charge 1002 in FIG. 10), compressor 130-1will compress working fluid flowing through it. As another example,during a slow rolling mode (e.g., CPT slow rolling 1062 in FIG. 15), thecompressor 130-1, though spinning (e.g., via torque from the turningmotor 121-1), may not cause an operationally significant increase inpressure of the working fluid.

Compressor 130-1 has at least one fluid inlet which connects to fluidinterconnect 20 and allows working fluid to enter the low-pressure sideof the compressor 130-1. Compressor 130-1 also has at least one fluidoutlet which connects to fluid interconnect 17 and allows working fluidto exit the high-pressure side of the compressor 130-1. The schematicillustration represented in FIG. 8 is not meant to limit the CPT system100 to a particular arrangement. For example, the turning motor 121-1may be oriented differently or located at a different location where itis still capable of turning the drivetrain 150. As another example,inlets and outlets to the turbomachinery may be located at sides otherthan the top, side, and ends depicted.

A variable frequency drive (“VFD”) (e.g., VFD 214 in FIG. 9) may beshared between the CPT system 100 and the GPT system 200. In oneembodiment, the VFD may be utilized for startup and slow-rolling of thesystem only and is configured to exert only positive loads on thedrivetrain 150. For example, VFD 214 may provide variable frequencypower to motor 110-1 during CPT system 100 spinup.

Depending on operational mode and state, turbine 140-1 may reduce thepressure (e.g., through expansion) of working fluid flowing through theturbine 140-1, and energy derived from that pressure reduction may betransformed into rotational energy in the drivetrain 150. Turbine 140-1has a fluid inlet which connects to fluid interconnect 18 and allowsworking fluid to enter the high-pressure side of the turbine 140-1.Turbine 140-1 also has a fluid outlet which connect to fluidinterconnect 19 and allows working fluid to exit the low-pressure sideof the turbine 140-1.

B. Generation Powertrain Subsystem

FIG. 7 is a schematic diagram of the generation powertrain system 200,according to an example embodiment. FIG. 7 provides additional detailconcerning GPT system 200 than is shown in the top-level schematic ofFIG. 2. The GPT system 200 may be implemented in PHES systems disclosedherein, including the PHES system 1000 embodiment illustrated in FIG. 2.Other embodiments of a generation powertrain system operable in PHESsystems disclosed herein are possible as well.

In FIG. 7, GPT system 200 includes a generator 210-1 as part of thegenerator system 210 of FIG. 2, a gearbox 220-1 as part of thegeneration gearbox system 220 of FIG. 2, a compressor 230-1 as part ofgeneration compressor system 230, and a turbine 240-1 as part ofgeneration turbine system 240. These components are connected via adrivetrain 250, such that the generator 210-1 is capable of being drivenby the gearbox 220-1 and the turbine 240-1, and vice-versa. Depending onoperational mode and system states, the generator system 210, andgenerator 210-1, may generate net positive electrical power that is thesent outside and/or elsewhere within the PHES system 1000. Additionally,depending on the operating condition and state, the generator 210-1 mayact as a motor. For example, during spinup of the GPT system 200, thegenerator 210-1 may receive electrical power and drive the gearbox 220-1and the turbomachinery. Drivetrain 250 may include a fixed connectionbetween compressor 230-1 and turbine 240-1, and/or may include one ormore shafts, flexible couplings, clutches, and/or gearboxes betweencompressor 230-1 and turbine 240-1.

GPT system 200 further includes a turning motor 221-1 that is capable ofdriving the compressor 230-1 and the turbine 240-1. Within GPT system200, gearbox 220-1 provides a speed conversion between the generator210-1 and turning motor 221-1 and the turbomachinery. In otherembodiments of a generation powertrain system, the gearbox 220-1 may actonly on one of the generator 210-1 and turning motor 221-1.Alternatively or additionally, gearbox 220-1 may act only on generator210-1 and another gearbox (or no gearbox) may act on turning motor221-1. In another embodiment, gearbox 220-1 may be omitted, thereforeresulting in no speed conversion

Turning motor 221-1 may be used for spinning GPT system 200turbomachinery under slow roll, for example, to cool the turbine 240-1following a shutdown, and before bringing the rotating equipment torest. The turning motor 221-1 may be mounted to the gearbox 220-1 or thedrivetrain 250 or the generator 210-1, or elsewhere, and preferablyrotates the turbomachinery at a very low RPM compared to normaloperational speed of the turbomachinery. The turning motor 221-1 isfitted with an overrunning clutch 221-2 that disengages when thedrivetrain 250 side of the clutch is operating at higher speeds. Thisresults in the turning motor 221-2 engaging with the drivetrain 250 whenthe slowing drivetrain 250 reaches the speed of the turning motor 221-1.The turning motor 221-1 will then maintain the slow roll speed.

GPT system 200 may send electrical power out of, and receive power into,the subsystem via electrical interconnect 21 and via power interface2002. Depending on operational mode, state, and embodimentconfiguration, the power interface 2002 may receive electrical powerfrom the generator 210-1 via electrical interconnect 21A and sendelectrical power to an external source, such as an electrical grid orother load via electrical interconnect 27. The power interface 2002 mayalso send electrical power from an electrical grid or other source toGPT system 200. The power interface 2002 may alternatively oradditionally route power received from the GPT system 200 to the CPTsystem 100.

Depending on operational mode and state, compressor 230-1 may raise thepressure of working fluid flowing through the compressor 230-1 by usingrotational energy transmitted through the drivetrain 250 from, e.g., theturbine 240-1. For example, during a generation mode (e.g., generation1004 in FIG. 10), compressor 230-1 will compress working fluid flowingthrough it. As another example, during a slow rolling mode (e.g., GPTslow rolling 1054 in FIG. 14), the compressor 230-1, though spinning(e.g., via torque from the turning motor 221-1), may not cause anoperationally significant increase in pressure of the working fluid.Compressor 230-1 has a fluid inlet which connects to fluid interconnect26 and allows working fluid to enter the low-pressure side of thecompressor 230-1. Compressor 230-1 also has a fluid outlet whichconnects to fluid interconnect 22 and allows working fluid to exit thehigh-pressure side of the compressor 230-1. The schematic illustrationrepresented in FIG. 7 is not meant to limit the GPT system 200 to aparticular arrangement. For example, the turning motor 221-1 may beoriented differently or located at a different location where it isstill capable of turning the drivetrain 250. As another example, inletsand outlets to the turbomachinery may be located at sides other than thetop, side, and ends depicted.

As previously disclosed, a VFD (e.g., VFD 214 in FIG. 9) may be sharedbetween the CPT system 100 and the GPT system 200. In one embodiment,the VFD may be utilized for startup and slow-rolling of the system onlyand is configured to exert only positive loads on the drivetrain 250.For example, VFD 214 may provide variable frequency power to generator210-1 during GPT system 200 startup.

Depending on operational mode and state, turbine 240-1 may reduce thepressure (e.g., through expansion) of working fluid flowing through theturbine 240-1, and energy derived from that pressure reduction may betransformed into rotational energy in the drivetrain 250. In some modesand states, that rotational energy may be used to rotate the compressor230-1 and/or generate electrical power at the generator 210-1. Turbine240-1 has one or more fluid inlets which connect to fluid interconnect23 and allow working fluid to enter the high-pressure side of theturbine 240-1. Turbine 240-1 also has a fluid outlet which connects tofluid interconnect 25 and allows working fluid to exit the low-pressureside of the turbine 240-1.

C. Site Integration Subsystem

FIG. 9 is a schematic electrical diagram of a power interface, accordingto an example embodiment, that can be implemented in power interface2002 in site integration subsystem 2000. Power interface 2000 includes aVFD 214, a VFD-to-generator breaker 211, a generator-to-grid breaker212, a VFD-to-charge-motor breaker 111, and a charge-motor-to-gridbreaker 112, with each component in power interface 2002 electricallyconnected as illustrated. Breakers can be set to closed or open mode andmay be remotely controlled. Other embodiments of a power interface mayinclude additional or fewer breakers, additional or fewer VFDs,different electrical connections, and/or additional components.

For spinning up the GPT system 200, VFD-to-generator breaker 211 can beclosed to connect VFD 214 to generator system 210 (e.g., generator 210-1and/or turning motor 221-1), thus routing power from an external sourcevia electrical interconnect 27, through VFD 214, through breaker 211,and to generator system 210. For generation mode, generator-to-gridbreaker 212 can be closed to connect generator system 210 (e.g.,generator 210-1) to an external electrical grid or other external loadthrough electrical interconnects 21A and 27. For spinning up the CPTsystem 100, VFD-to-charge-motor breaker 111 can be closed to connect VFD214 to the motor system 110 (e.g., motor 110-1 and/or turning motor121-1) in the CPT system 100 through electrical interconnects 15A and27. For charge mode, charge-motor-to-grid breaker 112 can be closed toconnect motor system 110 (e.g., motor 110-1) in the CPT system 100 to anexternal electrical grid or other electrical power source throughelectrical interconnects 15A and 27.

D. Main Heat Exchanger Subsystem

FIGS. 6A and 6B are schematic fluid path diagrams of example embodimentsof main heat exchanger systems, that can be implemented as main heatexchanger system in a PHES system (e.g., PHES systems 1000, 1003, 1005).FIGS. 6A and 6B provide additional details, in separate embodiments,concerning main heat exchanger system 300A than is shown in thetop-level schematics of FIG. 2, 27 or 29.

The main heat exchanger system 390 embodiment in FIG. 6A and/or the mainheat exchanger system 391 embodiment in FIG. 6B can be implemented asthe main heat exchanger system 300A in PHES systems 1000, 1003, 1005, orother disclosed PHES systems. Other main heat exchanger systemembodiments are also possible. References herein to main heat exchangersystem 300A can be understood with reference to embodiments 390 and/or391.

In general terms, main heat exchanger system 300A consists of fourdifferent heat exchanger systems, but all operate together within a PHESsystem, such as PHES systems 1000, 1003, 1005 to provide the desiredoperating conditions for operational modes. Each heat exchanger systemconsists of one or more heat exchanger units that may be connected viamanifolds and/or other fluid routing systems.

The main heat exchanger system 300A has two major modes of operation,mirroring the PHES system main modes of operation. During PHES systemgeneration (e.g., generation 1004 in FIG. 10), the heat exchangers canoperate in a forward flow direction at a flow rate between a maximumpower (operational maximum) mass flow rate and a maximum turndown(operational minimum) mass flow rate. In this generation mode, heat istransferred from an HTS medium to a working fluid at HHX system 500,from the working fluid to a CTS medium at CHX system 600, from alow-pressure working fluid stream to a high-pressure working fluidstream at RHX system 400, and from the working fluid to the ambientenvironment or other heat sink at AHX system 700. During PHES systemcharge (e.g., charge 1002 in FIG. 10), the heat exchangers operate inthe reverse flow direction at a flow rate between the maximum power massflow rate and the maximum turndown mass flow rate. In this process, heatis transferred from the working fluid to the HTS medium at HHX system500, from the CTS medium to the working fluid at CHX system 600, andfrom a high-pressure working fluid stream to a low-pressure workingfluid stream at RHX system 400.

Under some PHES system modes, such as a long term Cold Dry Standby 1010(see FIG. 10), the HTS medium and the CTS medium in the main heatexchanger system 300A is drained to thermal reservoirs (e.g., CTS system691 and/or 692, and/or HTS system 591 and/or 592). In such a scenario,heat traces may be used to ensure that the HTS medium does not freeze.

Main heat exchanger system 300A includes CHX system 600. A function ofCHX system 600 is to transfer heat between a CTS medium and a workingfluid. As illustrated in FIGS. 6A and 6B, embodiments of CHX system 600can include differing amounts of cold-side heat exchangers (“CHX”)depending on design requirements. CHX system 600 is illustrated asincluding cold-side heat exchangers 600-1, 600-2, through 600-n, whichreflect in these example embodiments 390, 391 at least three CHX and caninclude more than three CHX, although other PHES system embodiments mayhave less than three CHX. In some embodiments, as illustrated in FIGS.6A and 6B, each of CHX 600-1 through 600-n is a cross-flow heatexchanger. Specifically, a CTS medium flows through each of CHX 600-1through 600-n between fluid interconnect 1 and fluid interconnect 13.Additionally, a working fluid flows through each of CHX 600-1 through600-n between fluid interconnect 2 and fluid interconnect 14. In anotherembodiment, one or more CHX may not be cross-flow, and may have anotherinternal fluid routing arrangement; however, CTS flow betweeninterconnects 1, 13 and working fluid flow between interconnects 2, 14is maintained.

As illustrated in FIGS. 6A and 6B, each of CHX 600-1 through 600-n isconnected in parallel to the CTS medium and working fluid flows,respectively, with respect to each other CHX. In another embodiment, oneor more CHX may be connected in series with one or more CHX. In anotherembodiment, one more groups of CHX may be connected in parallel, and oneor more groups of CHX may be connected in series. In another embodiment,individual CHX and/or groups of CHX may be combined in variouscombinations of series and parallel configurations.

Main heat exchanger system 300A includes HHX system 500. A function ofHHX system 500 is to transfer heat between an HTS medium and a workingfluid. Embodiments of HHX system 500 can include differing amounts ofhot-side heat exchangers (“HHX”) depending on design requirements. HHXsystem 500 is illustrated as including hot-side heat exchangers 500-1,500-2, through 500-n, which reflect in these example embodiments 390,391 at least three HHX and can include more than three HHX, althoughother PHES system embodiments may have less than three HHX. In someembodiments, as illustrated in FIGS. 6A and 6B, each of HHX 500-1through 500-n is a cross-flow heat exchanger. Specifically, an HTSmedium flows through each of HHX 500-1 through 500-n between fluidinterconnect 6 and fluid interconnect 8. Additionally, a working fluidflows through each of HHX 500-1 through 500-n between fluid interconnect7 and fluid interconnect 9. In another embodiment, one or more HHX maynot be cross-flow, and may have another internal fluid routingarrangement; however, HTS flow between interconnects 6, 8 and workingfluid flow between interconnects 7, 9 is maintained.

As illustrated in FIGS. 6A and 6B, each of HHX 500-1 through 500-n isconnected in parallel to the HTS medium and working fluid flows,respectively, with respect to each other HHX. In another embodiments,one or more HHX may be connected in series with one or more HHX. Inanother embodiments, one more groups of HHX may be connected inparallel, and one or more groups of HHX may be connected in series. Inanother embodiment, individual HHX and/or groups of HHX may be combinedin various combinations of series and parallel configurations.

Main heat exchanger system 300A includes RHX system 400. A function ofRHX system 400 is to transfer heat between a high-pressure working fluidstream and a low-pressure working fluid stream. Embodiments of RHXsystem 400 can include differing amounts of recuperator heat exchangers(“RHX”) depending on design requirements. In FIGS. 6A and 6B, RHX system400 is illustrated as including recuperator heat exchangers 400-1,400-2, through 400-n, which reflect at least three RHX and can includemore than three RHX in these example embodiments, 390, 391 althoughother PHES system embodiments may have less than three RHX. In someembodiments, as illustrated in FIGS. 6A and 6B, each of RHX 400-1through 400-n is a cross-flow heat exchanger. Specifically, workingflows through each of RHX 400-1 through 400-n between fluid interconnect5 and fluid interconnect 11. Additionally, the working fluid in adifferent part of the working fluid loop flows through each of RHX 400-1through 400-n between fluid interconnect 10 and fluid interconnect 12.In another embodiment, one or more RHX may not be cross-flow, and mayhave another internal fluid routing arrangement; however, working fluidflow between interconnects 5, 11 and working fluid flow betweeninterconnects 10, 12 is maintained.

As illustrated in FIGS. 6A and 6B, each of RHX 400-1 through 400-n isconnected in parallel to the working fluid flows with respect to eachother RHX. In another embodiments, one or more RHX may be connected inseries with one or more RHX. In another embodiments, one more groups ofRHX may be connected in parallel, and one or more groups of RHX may beconnected in series. In another embodiment, individual RHX and/or groupsof RHX may be combined in various combinations of series and parallelconfigurations.

Main heat exchanger system 300A includes AHX system 700. A function ofAHX system 700 is to transfer heat from a working fluid to the ambientenvironment, or other external heat sink, during generation mode. In oneembodiment, the AHX system 700 will only be operational during PHESsystem generation (e.g., generation 1004 in FIG. 10). For example,during PHES system charge (e.g., charge 1002 in FIG. 10), the AHX system700 will be bypassed, as further discussed herein.

Embodiments of AHX system 700 can include differing configurations andamounts of ambient heat exchangers (“AHX”) (also referred to as ambientcoolers) depending on design requirements. In embodiment 390 in FIG. 6A,AHX system 700 is illustrated as including ambient heat exchangers700-1, 700-2, through 700-n, which reflect at least three AHX in thisexample embodiment and can include more than three AHX, although otherPHES system embodiments may have less than three AHX. In a preferredembodiment, AHX system 700 includes only one AHX, e.g., AHX 700-1. Inembodiment 390, as illustrated in FIG. 6A, each of AHX 700-1 through700-n is an ambient cooler that exhausts heat to the environment fromthe working fluid flowing through the AHX between fluid interconnects 4and 3. In the embodiment of FIG. 6A, fluid interconnects 28, 29 are notutilized. In the embodiment of FIG. 6A, individual AHX may include oneor more variable-speed fans that can be controlled to adjust ambient airflow across the AHX in order to reach a desired working fluid outlettemperature of the AHX system 700. As illustrated in FIG. 6A, each ofAHX 700-1 through 700-n is connected in parallel to the working fluidflow with respect to each other AHX. In another embodiments, one or moreAHX may be connected in series with one or more AHX. In anotherembodiments, one more groups of AHX may be connected in parallel, andone or more groups of AHX may be connected in series. In anotherembodiment, individual AHX and/or groups of AHX may be combined invarious combinations of series and parallel configurations.

In embodiment 391 in FIG. 6B, AHX system 700 is illustrated as includingambient heat exchangers 701-1, 701-2, through 701-n, which reflect atleast three AHX in this example embodiment and can include more thanthree AHX, although other PHES system embodiments may have less thanthree AHX. In a preferred embodiment, AHX system 700 includes only oneAHX, e.g., AHX 701-1. In embodiment 391, as illustrated in FIG. 6B, eachof AHX 701-1 through 701-n is a cross-flow heat exchanger. Specifically,a heat sink fluid flows through each of AHX 701-1 through 701-n betweenfluid interconnect 28 and fluid interconnect 29. Additionally, a workingfluid flows through each of AHX 701-1 through 701-n between fluidinterconnect 4 and fluid interconnect 3. In the embodiment of FIG. 6B,the heat sink fluid may be ambient air that is pulled from and/or isexhausted to the environment, or the heat sink fluid may be a fluid thatis pulled from a heat sink fluid reservoir (not shown) and/or sent toheat sink fluid reservoir (not shown) or other heat sink (not shown),such as a thermal waste heat capture/transfer system. In embodiment 391of FIG. 6B, heat sink fluid mass flow rate through the AHXs may beadjusted in order to reach a desired working fluid outlet temperature ofthe AHX system 700. As illustrated in FIG. 6B, each of AHX 701-1 through701-n is connected in parallel to the working fluid flow with respect toeach other AHX. In another embodiments, one or more AHX may be connectedin series with one or more AHX. In another embodiments, one more groupsof AHX may be connected in parallel, and one or more groups of AHX maybe connected in series. In another embodiment, individual AHX and/orgroups of AHX may be combined in various combinations of series andparallel configurations.

Main heat exchanger system 300A, as illustrated in embodiment 390 and391 in FIGS. 6A and 6B, may include heat traces 460 and 560 as part ofthe RHX system 400 and HHX system 500, respectively. A function of heattrace 460 is to maintain fluid manifolds and/or other metal mass atdesired setpoint temperatures during various modes and/or states, forexample, in order to reduce thermal gradients on sensitive components. Afunction of heat trace 560 is to maintain fluid manifolds and/or othermetal mass at desired setpoint temperatures during various modes and/orstates, for example, in order to avoid freezing (i.e., phase change) ofHTX medium in the HHX system 500 and/or to reduce thermal gradients onsensitive components. Each of the heat traces 460 and 560 can functionto reduce thermal ramp rates, which benefits heat exchanger longevity,and allows for faster PHES system (e.g., PHES systems 1000, 1003, 1005)startup times. Heat traces 460 and 560 are illustrated as near fluidinterconnects 12 and 9, respectively. However, heat traces 460 and 560can be located at other locations within RHX system 400 and HHX system500 in order to accomplish their functions. Additionally oralternatively, heat traces 460 and 560 can include heat traces atmultiple locations within RHX system 400 and HHX system 500 in order toaccomplish their functions.

E. Working Fluid Loop Subsystem

FIG. 3 is a schematic fluid path diagram of a working fluid loop 300which may be implemented in a PHES system, such as PHES system 1000,according to an example embodiment. FIG. 3 provides additional detailconcerning working fluid loop 300 than is shown in the top-levelschematic of FIG. 2. In general terms, the working fluid loop 300includes, for example, high-pressure fluid paths and low-pressure fluidpaths separated by the turbomachinery, turbomachinery bypass andrecirculation loops, heat exchangers (e.g., excess heat radiators),valves, pressure relief devices, working fluid supply components (e.g.,working fluid compressor), an inventory control system including workingfluid tank systems (e.g., high pressure tank systems and low pressuretank systems), and sensors for pressure, temperature, flow rate,dewpoint, speed, and/or fluid concentration. Other embodiments of aworking fluid loop operable in PHES systems disclosed herein arepossible as well.

FIG. 3N and FIG. 3O illustrate circulatory flow paths of working fluidin working fluid loop 300 for charge mode 1002 and generation mode 1004,respectively. Bold fluid paths illustrate the circulatory flow paths andarrows on bold fluid paths indicate circulatory flow direction. Workingfluid may be resident in other fluid paths, but is not activelycirculating because such other fluid paths do not form a circulatorycircuit with an inlet and outlet (i.e., they are a dead end). Valvepositions are indicated with a filled valve icon representing a closedvalve, an unfilled valve icon representing an open valve, and across-hatched valve representing a valve that may change position statewithout affecting the illustrated circulatory flow path. For example, inFIG. 3N, valve 231 is closed, valve 131 is open, and valve 242 maychange position state without affecting the flow path.

The embodiment of working fluid loop 300 illustrated in FIG. 3 can servenumerous roles within PHES system 1000. The working fluid loop 300 canroute working fluid between the turbomachinery and the heat exchangers.The working fluid loop 300 can provide working fluid to the main heatexchanger system 300A for transferring heat between HTS medium and CTSmedium during, for example, charge or generation cycles. The workingfluid loop 300 can protect the turbomachinery during emergency tripevents, and help with compressor surge prevention and overpressureprevention. The working fluid loop 300 can maintain its pressures (e.g.,pressures in low-pressure and high-pressure fluid paths) below specifiedset points for each mode of PHES system operation. The working fluidloop 300 can help with smooth PHES system 1000 startup and shutdown,including, for example, working fluid bypass flow during generationcycle startup to prevent bidirectional loads/demands on a VFD. Theworking fluid loop 300 can quickly bring working fluid pressures down toallow mode switching operation within short time intervals. The workingfluid loop 300 can maintain working fluid loop pressures at or above aminimum working fluid loop base pressure, such as whenever CHX system600 or HHX system 500 are filled with their respective CTS or HTS media,for example, to prevent leakage of CTS or HTS media into the workingfluid loop 300. The working fluid loop 300 can adjust low-side pressurein the working fluid loop between a minimum pressure and workingpressures (i.e. pressures during charge and generation), as a means ofcontrolling PHES system power. The working fluid loop 300 can regulatecirculate working fluid mass, for example to control PHES systempressures, PHES system power, and/or compensate for working fluid lossesfrom the working fluid loop over time.

The following paragraphs describe components of a working fluid loop,such as working fluid loop 300, or working fluid loops 300C or 300D asappropriate.

Pressure relief device 101 is a pressure relief device on a low-pressurelow-temperature (“LPLT”) portion of the working fluid loop 300. Itprotects from overpressure the LPLT portion of the working fluid loop inthe vicinity, for example, where high-pressure working fluid could beintroduced through the turbomachinery, recirculation valves, or bypassvalves.

Pressure relief device 102 is a pressure relief device on a low-pressuremedium-temperature (“LPMT”) portion of the working fluid loop 300. Itprotects from overpressure the LPMT portion of the working fluid loop300 in the vicinity, for example, where high-pressure working fluidcould be introduced through the turbomachinery, recirculation valves,and/or bypass valves.

Valve 119 regulates a high-flow recirculation fluid path around acompressor system (e.g., compressor system 130, compressor system 830,reversible turbomachine system 850) that can be opened, for example, toreduce and/or prevent surge in the compressor system. For example, valve119 may be opened following a trip event during charge mode operation orwhen valve 131 is closed. In an embodiment where valve 132 issufficiently large, valve 119 can be omitted.

Valve 131 is a compressor system (e.g., compressor system 130,compressor system 830, reversible turbomachine system 850) shutoff valvethat, when closed, isolates the compressor system from the high-pressureside of the working fluid loop (e.g., working fluid loops 300, 300C,300D) for example, during generation mode or following a trip event.Valve 131 preferably fails closed. A benefit of valve 131 is that it canbe closed to isolate the compressor system from the large, high-pressureworking fluid volume that is present in fluid paths on the side of valve131 opposite the compressor system. That large volume could cause thecompressor system to surge if the compressor system were to spin downfollowing a power loss or unexpected trip scenario in the PHES system(e.g., PHES system 1000, 1003, 1005).

Valve 132 regulates a recirculation fluid path around a compressorsystem (e.g., compressor system 130, compressor system 830, reversibleturbomachine system 850) that can be opened, for example, to recirculateworking fluid driven by the compressor system during, for example,cooldown (e.g., during slow rolling) or after a mode switch. Valve 132may exhibit slow response time and preferably fails open. A benefit offailing open is that a valve failure does not prevent compressor systemcooldown, which is beneficial to prevent damage to the compressorsystem.

Heat exchanger 132H is a radiator in the recirculation fluid pathregulated by valve 132 and removes heat (e.g., to ambient) from theworking fluid recirculating through a compressor system (e.g.,compressor system 130, compressor system 830, reversible turbomachinesystem 850), for example, following the end of charge mode operation.

Valve 133 is a working fluid dump valve located downstream of acompressor system (e.g., compressor system 130, compressor system 830,reversible turbomachine system 850) and isolation valve 131. Valve 133may be, for example, used to reduce the working fluid pressure in thevicinity of the outlet of the compressor system during certain events,for example trip events during charge mode 1002. Opening valve 133 dumpsworking fluid to ambient, or a working fluid reservoir (not shown), anddecreases working fluid pressure in the vicinity of the outlet of thecompressor system, which beneficially reduces the risk of compressorsystem surge.

Valve 141 is a charge turbine system 140 shutoff valve that, whenclosed, isolates charge turbine system 140 from the high-pressure sideof the working fluid loop 300, for example, during generation mode orfollowing a trip event. Valve 141 preferably fails closed. A benefit ofvalve 141 is that it can be closed, in conjunction with closing valve131, to prevent working fluid mass moving from the high-pressure side ofthe main working fluid loop 300 to the low-pressure side of the workingfluid loop 300, which could result in the working fluid loop 300equilibrating in pressure to a settle-out pressure greater than thepressure rating of components in the low-pressure side of the loop.

Valve 142 regulates a recirculation fluid path around a turbine system(e.g., turbine system 140, reversible turbomachine system 852) that canbe opened, for example, to recirculate working fluid through the turbinesystem during, for example, turning (e.g., slow rolling) or after a modeswitch. Valve 142 may exhibit slow response time and preferably failsopen. A benefit of valve 142 is that it can be opened to prevent theinlet pressure of the turbine system from dropping substantially belowthe outlet pressure of the turbine system upon closing valve 141 or 841,which is beneficial because it prevents the turbine system fromoperating outside typical design specifications for pressuredifferentials.

Fan 142F can be operated, when valve 142 is open, to providerecirculation flow of working fluid through the turbine system (e.g.,turbine system 140, reversible turbomachine system 852) via therecirculation loop controlled by valve 142. This is beneficial, forexample, when the spinning turbine system does not create appreciableworking fluid flow through the turbine system and consequentlyexperiences windage. Fan 142 can be turned on to create working fluidflow through the turbine system via the recirculation loop to alleviatethe windage.

Valve 222 regulates a bypass fluid path that can be opened, for exampleduring generation mode, to provide a working fluid bypass path aroundthe high-pressure side of RHX system 400 and HHX system 500, therebyallowing some amount of working fluid flow through the bypass fluid pathinstead of through RHX system 400 and HHX system 500. Opening valve 222,preferably in conjunction with, e.g., closing valves 231, 241, or valves831C1, 831G1, 841C1, 841G1, or valves 831, 841, removes energy (in theform of hot compressed working fluid) that is supplied to a turbinesystem (e.g., turbine system 240, turbine system 840, reversibleturbomachine system 852), thereby starving the turbine system.Beneficially, valve 222 can be opened, for example, when a PHES system(e.g., PHES system 1000, 1003, 1005) in generation mode experiences aloss of load event (e.g., from the electric grid) or a trip event.Closing valves 231 and 241, or valves 831C1, 831G1, 841C1, 841G1, orvalves 831, 841, and opening of 222 collectively can prevent overspeedof the generation mode powertrain (e.g., GPT system 200, or sharedpowertrain system 800, or reversible powertrain system 801) as a resultof turbine system overspeed.

Valve 229 regulates a bypass fluid path that can be opened to provide ahigh-flow working fluid bypass path around the high-pressure side of RHXsystem 400, HHX system 500, and a turbine system (e.g., turbine system240, turbine system 840, reversible turbomachine system 852), therebyallowing some amount of working fluid flow through the bypass fluid pathinstead of through RHX system 400, HHX system 500, and the turbinesystem. Beneficially, valve 229 can be opened to reduce load duringstartup of generation mode and to prevent the generation mode turbinesystem (e.g., turbine system 240, turbine system 840, reversibleturbomachine system 852) from generating substantial power duringstartup of generation mode. Opening valve 229 reduces a net loadrequired of a generation or motor/generator system (e.g., generatorsystem 210 acting as a motor, motor/generator system 810 acting as amotor) during generation mode startup. Opening valve 229 reduces acompressor system (e.g., compressor system 230, compressor system 830,reversible turbomachine system 850) power need by reducing outletpressure at the compressor system. Opening valve 229 also starves theturbine system (e.g., turbine system 240, turbine system 840, reversibleturbomachine system 852) of much of its fluid flow so that the turbinesystem does not produce substantially more power than the compressorsystem (e.g., compressor system 230, compressor system 830, reversibleturbomachine system 850). By keeping a low, but net positive, electricalpower demand from the generation or motor/generator system (e.g.,generator system 210 acting as a motor, motor/generator system 810acting as a motor) means that a VFD (e.g., VFD 214) supplying power tothe generation system can maintain speed control during startup/spin-up.Opening valve 229 also provides a high-flow fluid path to prevent surgein the compressor system (e.g., compressor system 230, compressor system830, reversible turbomachine system 850), for example, following a tripevent out of generation mode operation and when valve 231, or valves841C1 and 841G1, or valve 841, are closed.

Valve 231 is a generation compressor system 230 shutoff valve that, whenclosed, isolates generation compressor system 230 from the high-pressureside of the working fluid loop during charge mode operation or followinga trip event. Valve 231 preferably fails closed. A benefit of valve 231is that it can be closed to isolate the compressor system 230 from thelarge high-pressure working fluid volume that is present in fluid pathson the side of valve 231 opposite the compressor system 230. That largevolume could cause the compressor system 230 (e.g. compressor 230-1) tosurge if the compressor system 230 (e.g. compressor 230-1) were to spindown following a power loss or unexpected trip scenario in the PHESsystem 1000.

Valve 232 regulates a recirculation fluid path around a generationcompressor system (e.g., compressor system 240, reversible turbomachinesystem 852 acting as a compressor) that can be opened, for example, torecirculate working fluid driven by the generation compressor systemduring, for example, turning or after a mode switch. Valve 232 mayexhibit slow response time and preferably fails open. A benefit of valve232 failing open is that it allows for turbomachinery temperatureequilibration upon failure; for example, failure during a post-shutdownspinning mode allows cooldown of hot portions of the generationcompressor system and warmup of the inlet side of the generationcompressor system. In a shared powertrain working fluid loop, such asworking fluid loop 300C in FIG. 28B, valve 132 may be used similarly orthe same as valve 232. In such a configuration, valve 132 may regulate arecirculation fluid path around compressor system 830 that can beopened, for example, to recirculate working fluid driven by compressorsystem 830 during, for example, turning or after a mode switch. In sucha configuration, valve 132 may exhibit slow response time and preferablyfails open. A benefit of valve 132 in such a configuration failing openis that it allows for turbomachinery temperature equilibration uponfailure; for example, failure during a during a post-shutdown spinningmode allows cooldown of hot portions of the compressor system 830 andwarmup of the inlet side of the compressor system 830.

Valve 241 is generation turbine system 240 shutoff valve that, whenclosed, isolates generation turbine system 240 from the high-pressureside of the working fluid loop 300 during, for example, charge modeoperation or following a trip event. In practical effect, closing valve241 can starve turbine system 240 and prevent GPT system 200 overspeed.Valve 241 preferably fails closed. A benefit of valve 241 is that can beclosed to isolate a source of high-pressure working fluid that couldcontinue to drive the turbine system 240 during, for example, aloss-of-grid-load event, which otherwise might cause an overspeed eventfor the GPT system 200.

Valve 242 regulates a recirculation fluid path around a generation modeturbine system (e.g., turbine system 240, reversible turbomachine system850 acting as a turbine) that can be opened, for example, to recirculateworking fluid through the turbine system during, for example, cooldown(e.g. during slow rolling) or after a mode switch. Valve 242 may exhibitslow response time and preferably fails open. A benefit of valve 242failing open is that if valve 242 fails, by failing open it allows forcooldown spinning of the powertrain system (e.g., GPT system 200,reversible powertrain system 801) after shutdown of the powertrainsystem. Cooldown spinning can prevent bowing of rotating components inthe turbomachinery. Another benefit of valve 242 failing open is that,when failed open, the powertrain system (e.g., GPT system 200,reversible powertrain system 801) can continue to function duringgeneration (e.g., mode 1004) or slow turning (e.g., mode 1006), albeitwith decreased efficiency during generation due to open valve 242creating a bleed path for the working fluid.

Heat exchanger 242H is a radiator in the recirculation fluid pathregulated by valve 242 or valve 842 and removes heat (e.g., to ambient)from the working fluid recirculating through a turbine system (e.g.,turbine system 240, turbine system 840, reversible turbomachine system852).

Fan 242F can be operated, when valve 142 is open, to providerecirculation flow of working fluid through a turbine system (e.g.,turbine system 240, reversible turbomachine system 852) via therecirculation loop controlled by valve 242. This is beneficial, forexample, when the spinning turbine system does not create appreciableworking fluid flow through the turbine system and consequentlyexperiences windage. Fan 242 can be turned on to create working fluidflow through the turbine system via the recirculation loop to alleviatethe windage and/or for cooling down of turbine system during, forexample, slow rolling.

Valve 323 regulates a bypass fluid path that can be opened, for exampleduring charge mode, to provide a working fluid bypass path around AHXsystem 700, thereby allowing some amount of working fluid flow throughthe bypass fluid path instead of through AHX system 700. Beneficially,opening valve 323, preferably in conjunction with closing valve 324 (andvalve 325 if present), diverts working fluid around AHX system 700,thereby reducing working fluid loop 300 pressure drop when heat dumpfrom the working fluid is not desired, such as during charge modeoperation. Valve 323 may exhibit slow actuation time and preferablyfails open. Beneficially, valve 323 preferably fails open so thatworking fluid loop 300 can maintain flow if working fluid valve 324 (andvalve 325 if present) is closed or were to fail closed. If valve 323 andvalve 324 (or valve 325 if present) are both closed, working fluidcirculation in the working fluid loop 300 would stop and the loss ofworking fluid flow could damage turbomachinery attempting to circulatethe working fluid. Additionally, if valve 323 fails open, it allows thePHES system (e.g., PHES system 1000, 1003, 1005) to continue operating,albeit with a loss of efficiency in some modes. In an alternativeembodiment of a working fluid loop, valve 323 may be combined with valve324, for example at the junction of the fluid path exiting interconnect5 and the fluid path entering interconnect 4 in generation mode, as atwo-position, three-way valve to accomplish the same effect as the twovalves 323, 324.

Valve 324 is an isolation valve that, when closed, isolates AHX system700 from circulation of working fluid through AHX system 700, forexample during charge mode. If valve 325 is present, both valves 324 and325 may be closed to completely isolate AHX system 700 from workingfluid, for example during charge mode and/or service. Valve 324 mayexhibit slow actuation time and preferably fails to current position oralternately fails open. Beneficially, if valve 324 fails to currentposition, the PHES system (e.g., PHES system 1000, 1003, 1005) cancontinue its current operation. Alternatively, valve 324 can bespecified to fail open for the reasons described above with respect tovalve 323.

Valve 325 is an isolation valve that, when closed, isolates AHX system700 from circulation of working fluid through AHX system 700, forexample during charge mode. Valve 325 may exhibit slow actuation timeand preferably fails to current position. Beneficially, if valve 325fails to current position, the PHES system (e.g., PHES system 1000,1003, 1005) can continue its current operation. In an alternativeembodiment, valve 325 may be omitted from working fluid loop 300. FIGS.3K, 3L and their corresponding disclosure illustrate that embodiment. Inthis alternate embodiment with valve 325 omitted, closing valve 324 andopening valve 323 will cause working fluid to not circulate through AHXsystem 700, and instead bypass AHX system 700 through valve 323.However, omitting valve 325 means that AHX system 700 cannot be fullyisolated from the working fluid loop (e.g., working fluid loops 300,300C, 300D), as it will see resident working fluid.

Filter 301 is a working fluid filter (or pre-filter) for working fluidcompressor 303 that provides filtration of working fluid entering theworking fluid loop (e.g., working fluid loops 300, 300C, 300D) from anoutside source, such as ambient air when air is the working fluid or fora working fluid that is stored in an outside working fluid make-upreservoir (not shown). Filter 301 may act as a pre-filter if workingfluid compressor 303 also contains filters.

Valve 302 is a working fluid compressor 303 feed valve that, whenopened, provides the ability for the working fluid compressor 303 topull working fluid from ambient or an outside working fluid make-upreservoir (not shown). When closed, valve 302 provides the ability forthe working fluid compressor 303 to pull working fluid from the workingfluid loop (e.g., working fluid loops 300, 300C, 300D) (e.g., fromevacuation lines via the fluid paths through valve 304 or valve 305).

Working fluid compressor 303 is a make-up working fluid compressor. Whenactivated, working fluid compressor 303 can, depending on valve states,provide working fluid for inventory control system (“ICS”) 300B storagetank systems 310 and/or 320. Additionally or alternatively, whenactivated, working fluid compressor 303 can, depending on valve states,replenish a working fluid loop (e.g., working fluid loops 300, 300C,300D) with working fluid lost through leakage or venting. Additionallyor alternatively, when activated, working fluid compressor 303 can,depending on valve states, evacuate the working fluid loop to reducepressure below what ICS 300B valve arrangements can accomplish whenlowering the working fluid loop pressure below the settle-out pressurefor startup. This is beneficial because the working fluid loop may bepreferably partially evacuated (depending, e.g., on pressure limitationsof the CPT system 100 vs. The GPT system 200) in order to drop workingfluid loop pressure when one powertrain (e.g., CPT system 100 or GPTsystem 200) has spun down and the other power train is spinning up. Forexample, if PHES system 1000 is coming out of charge mode 1002 and CPTsystem 100 has just spun down, it is desirable to lower the workingfluid loop 300 pressure so that GPT system 200 can start to spin up.“Settle-out” pressure can be interpreted as the resulting pressure inthe working fluid loop if working fluid mass were allowed to move fromthe high-pressure side of the working fluid loop to the low-pressureside of the working fluid loop to the point where the pressure on bothsides equilibrated. Additionally or alternatively, when activated,working fluid compressor 303 can, depending on valve states, counteracthysteresis in the functioning of ICS 300B by pumping working fluid massfrom the low-pressure side of the working fluid loop to high-pressuretank system 320.

Valve 304 is a feed valve for the working fluid compressor 303 on alow-pressure-side evacuation fluid path of a working fluid loop (e.g.,working fluid loops 300, 300C, 300D). Valve 304, when open, connects thelow-pressure side of the working fluid loop to working fluid compressor303 for pulling working fluid from the working fluid loop into ICS 300Bhigh-pressure tank system 320.

Valve 305 is a feed valve for the working fluid compressor 303 on ahigh-pressure-side evacuation fluid path of a working fluid loop (e.g.,working fluid loops 300, 300C, 300D). Valve 305, when open, connects thehigh-pressure side of the working fluid loop to working fluid compressor303 for pulling working fluid from the working fluid loop into ICS 300Bhigh-pressure tank system 320.

Valve 308 is an evacuation valve on the low-pressure side of a workingfluid loop (e.g., working fluid loops 300, 300C, 300D). Valve 308, whenopen, allows working fluid in the working fluid loop to be evacuated tothe environment or an outside working fluid make-up reservoir (notshown). Valve 308 is primarily for servicing of the working fluid loop,but can also be used for inventory control purposes (e.g., reducingworking fluid mass in the working fluid loop) related to powergeneration mode 1004, charge mode 1002, or other operations.

Pressure relief device 309 is an ICS 300B low-pressure-side pressurerelief device that protects low-pressure fluid paths in a working fluidloop (e.g., working fluid loops 300, 300C, 300D) from overpressurization, for example, near where high-pressure working fluid isintroduced by ICS 300B (e.g., via valve 322) into the low-pressure fluidpaths.

Low-pressure tank system 310 is an ICS 300B tank system that includesone or more tanks that store working fluid at low pressure (e.g., lessthan the pressure in high-pressure tank system 320, and/or less than thepressure in the high-pressure side of a working fluid loop (e.g.,working fluid loops 300, 300C, 300D)). Working fluid may be moved intolow-pressure tank system 310 from, for example, working fluid loop 300.Working fluid may be released from low-pressure tank system 310 into,for example, working fluid loop 300. Preferably, tank system 310includes built-in pressure relief devices.

Valve 311 is an ICS 300B HP-LP valve that, for example, when open,allows for release of high-pressure working fluid from the high-pressureside of a working fluid loop (e.g., working fluid loops 300, 300C, 300D)into the low-pressure tank system 310. Valve 311 may be a controlledproportional valve that is used, for example, for controlling PHESsystem 1000, 1003, 1005 power ramping rates.

Valve 312 is an ICS 300B LP-LP valve that, for example, when open,allows for movement of low-pressure working fluid between low-pressuretank system 310 and the low-pressure side of a working fluid loop (e.g.,working fluid loops 300, 300C, 300D).

Valve 314 is an evacuation valve on the high-pressure side of a workingfluid loop (e.g., working fluid loops 300, 300C, 300D). Valve 314, whenopen, allows working fluid in the working fluid loop to be evacuated tothe environment or an outside working fluid make-up reservoir (notshown). Valve 314 is primarily for servicing of working fluid loop, butcan also be used for inventory control purposes (e.g., reducing workingfluid mass in the working fluid loop) related to power generation mode1004, charge mode 1002, or other operations.

Valve 318 is a dump valve on the high-pressure side of a working fluidloop (e.g., working fluid loops 300, 300C, 300D). Valve 318, when open,allows working fluid in the high-pressure side of the working fluid loopto be dumped to the ICS 300B low-pressure tank system 310, loweringpressure in the working fluid loop. Beneficially, this preservesfiltered working fluid as opposed to evacuating working fluid throughvalves 308 or 314. Though similarly arranged in ICS 300B, valve 318 maydiffer from valve 311. Valve 318 may be a fast switched (i.e.,“bang-bang”) valve and/or may be larger than valve 311. This isbeneficial for moving high-pressure working fluid from the working fluidloop into the low-pressure tank system 310 at a much faster rate thanvalve 311 can accomplish, which may be preferred for certain modetransitions or trip events.

Pressure relief device 319 is an ICS 300B high-pressure-side pressurerelief device that protects high-pressure fluid paths in a working fluidloop (e.g., working fluid loops 300, 300C, 300D) from overpressurization.

High-pressure tank system 320 is an ICS 300B tank system that includesone or more tanks that store working fluid at high pressure (e.g.,higher than the pressure in low-pressure tank system 310, and/or higherthan the pressure in the low-pressure side of a working fluid loop(e.g., working fluid loops 300, 300C, 300D)). Working fluid may be movedinto high-pressure tank system 320 from, for example, the high-pressureside of the working fluid loop via ICS 300B valves (e.g., valve 321)and/or working fluid compressor 303. Working fluid may be released fromhigh-pressure tank system 320 into, for example, the low-pressure sideof the working fluid loop via ICS 300B valves (e.g., valve 322).Preferably, the high-pressure tank system 320 includes built-in pressurerelief devices.

Valve 321 is an ICS 300B HP-HP valve that, for example, when open,allows for movement of high-pressure working fluid between thehigh-pressure side of a working fluid loop (e.g., working fluid loops300, 300C, 300D) 300 and high-pressure tank system 320.

Valve 322 is an ICS 300B LP-HP valve that, for example, when open,allows for release of high-pressure working fluid from high-pressuretank system 320 into the low-pressure side of a working fluid loop(e.g., working fluid loops 300, 300C, 300D).

Sensors 119S, 130S, 131S, 132S, 140S, 141S, 142S, 229S, 230S, 231S,232S, 240S, 241S, 242S, 324S, 325S, 361S, 362S, 363S, 364S, 365S, 366S,and 367S are monitoring and reporting devices that can provide one ormore of pressure, temperature, flow rate, dewpoint, and/or fluidconcentration data to one or more control systems controlling and/ormonitoring conditions of a PHES system (e.g., PHES system 1000, 1003,1005).

Sensor 303S is a monitoring and reporting devices that can provide oneor more of compressor speed, pressure, temperature, and/or flow ratedata to one or more control systems controlling and/or monitoringconditions of a PHES system (e.g., PHES system 1000, 1003, 1005).

Sensors 310S and 320S are monitoring and reporting devices that canprovide one or more of pressure, temperature, dewpoint, and/or fluidconcentration data to one or more control systems controlling and/ormonitoring conditions of a PHES system (e.g., PHES system 1000, 1003,1005).

Valve 401 regulates a bypass fluid path that can be opened, for exampleduring generation mode, to provide a working fluid bypass path aroundthe low-pressure side of RHX system 400 and AHX system 700, therebyallowing some amount of working fluid flow through the bypass fluid pathinstead of through RHX system 400 and AHX system 700. Beneficially,valve 401 may be used in conjunction with valve 222, 323, 324 (and 325,if present) to mitigate a negative effect of opening valve 222. During,for example, generation mode 1004, opening valve 222 (with valves 231,241 closed, or valves 831C1, 831G1, 841C1, 841G1 closed, or valves831,841 closed), will cause the outlet temperature of a turbine system(e.g., turbine system 240, turbine system 840, reversible turbomachinesystem 852) to drop quickly. That results in circulation of colderworking fluid downstream of the turbine system that could shock (andpotentially damage) the downstream RHX system 400 and AHX system 700 ifthe colder working fluid were allowed to pass into those heatexchangers. Therefore, as an example, when valve 222 is opened, valve401 may also be opened and preferably valves 323, 324 (and 325, ifpresent) may be closed, so that the colder working fluid flow from theturbine system outlet bypasses around RHX system 400 and AHX system 700and flows instead to the inlet of the CHX system 600, which is expectingcolder working fluid.

HP/LP Working Fluid Paths

In a PHES system (e.g., PHES system 1000, 1003, 1005) working fluid loop(e.g., working fluid loops 300, 300C, 300D), high-pressure fluid pathsare downstream of a compressor system (e.g., compressor systems 130,230, compressor system 830, reversible turbomachine system 850 acting asa compressor, reversible turbomachine system 852 acting as a compressor)and upstream of a turbine system (e.g., turbine systems 140, 240,turbine system 840, reversible turbomachine system 850 acting as aturbine, reversible turbomachine system 852 acting as a turbine) (i.e.,between outlets of charge or generation compressor systems and inlets ofcharge or generation turbine systems, respectively). Low-pressure fluidpaths are downstream of the turbine system (e.g., turbine systems 140,240, turbine system 840, reversible turbomachine system 850 acting as aturbine, reversible turbomachine system 852 acting as a turbine) andupstream of the compressor system (e.g., compressor systems 130, 230,compressor system 830, reversible turbomachine system 850 acting as acompressor, reversible turbomachine system 852 acting as a compressor)(i.e., between outlets of charge or generation turbine systems andinlets of charge or generation compressor systems 130, 230,respectively).

For example, a high-pressure fluid path is between the CPT system 100compressor system 130 outlet and the CPT turbine system 140 inlet. InFIGS. 3 and 3N, that high-pressure fluid path encompasses fluidinterconnects 17, 7, 9, 10, 12, and 18. With reference to thecirculatory flow paths illustrated in bold in FIG. 3N, the portion ofthis high-pressure fluid path downstream of compressor system 130,encompassing fluid interconnects 17, 7 and ending at HHX system 500 canadditionally be considered a high-pressure high-temperature (e.g.,HP-HT) fluid path. Similarly, the portion of this high-pressure fluidpath downstream of HHX system 500, encompassing fluid interconnects 9,10, 12, 18, and ending at the inlet to turbine system 140 canadditionally be considered a high-pressure medium-temperature (e.g.,HP-MT) fluid path.

Another high-pressure fluid path is between the GPT system 200compressor system 230 outlet and the GPT turbine system 240 inlet. InFIGS. 3 and 3O, that high-pressure fluid path encompasses fluidinterconnects 22, 12, 10, 9, 7, and 23. With reference to thecirculatory flow paths illustrated in bold in FIG. 3O, the portion ofthis high-pressure fluid path downstream of compressor system 230,encompassing fluid interconnects 22, 12, and ending at RHX system 400can additionally be considered a high-pressure medium-temperature (e.g.,HP-MT) fluid path. Similarly, the portion of this high-pressure fluidpath downstream of RHX system 400, encompassing fluid interconnects 10,9, 7, 23, and ending at the inlet to turbine system 240 can additionallybe considered a high-pressure high-temperature (e.g., HP-HT) fluid path.

As another example, a high-pressure fluid path is between the sharedpowertrain system 800 compressor system 830 outlet and the sharedpowertrain system 800 turbine system 840 inlet. In FIGS. 28A and 28B,that high-pressure fluid path encompasses fluid interconnects 28, 7, 9,10, 12, and 29. With reference to the circulatory flow paths illustratedin bold in FIG. 28A, the portion of this high-pressure fluid pathdownstream of compressor system 830, encompassing fluid interconnects28, 7, and ending at HHX system 500 can additionally be considered ahigh-pressure high-temperature (e.g., HP-HT) fluid path. Similarly, theportion of this high-pressure fluid path downstream of HHX system 500,encompassing fluid interconnects 9, 10, 12, 29, and ending at the inletto turbine system 840 can additionally be considered a high-pressuremedium-temperature (e.g., HP-MT) fluid path. With reference to thecirculatory flow paths illustrated in bold in FIG. 28B, the portion ofthis high-pressure fluid path downstream of compressor system 830,encompassing fluid interconnects 28, 12, 10, 9, and ending at HHX system500 can additionally be considered a high-pressure medium-temperature(e.g., HP-MT) fluid path. Similarly, the portion of this high-pressurefluid path downstream of HHX system 500, encompassing fluidinterconnects 7, 29, and ending at the inlet to turbine system 840 canadditionally be considered a high-pressure high-temperature (e.g.,HP-HT) fluid path.

As another example, a high-pressure fluid path is between the reversiblepowertrain system 801 reversible turbomachine system 850 outlet, whenreversible turbomachine system 850 is acting as a compressor, and thereversible powertrain system 801 reversible turbomachine system 852inlet, when reversible turbomachine system 852 is acting as a turbine.In FIG. 30A, that high-pressure fluid path encompasses fluidinterconnects 34, 7, 9, 10, 12, and 35. With reference to thecirculatory flow paths illustrated in bold in FIG. 30A, the portion ofthis high-pressure fluid path downstream of reversible turbomachinesystem 850, encompassing fluid interconnects 34, 7, and ending at HHXsystem 500 can additionally be considered a high-pressurehigh-temperature (e.g., HP-HT) fluid path. Similarly, the portion ofthis high-pressure fluid path downstream of HHX system 500, encompassingfluid interconnects 9, 10, 12, 35, and ending at the inlet to reversibleturbomachine system 852 can additionally be considered a high-pressuremedium-temperature (e.g., HP-MT) fluid path.

As another example, the same high-pressure fluid path is between thereversible powertrain system 801 reversible turbomachine system 852outlet, when reversible turbomachine system 852 is acting as acompressor, and the reversible powertrain system 801 reversibleturbomachine system 850 inlet, when reversible turbomachine system 850is acting as a turbine. In FIG. 30B, that high-pressure fluid pathencompasses the same fluid interconnects 34, 7, 9, 10, 12, and 35. Withreference to the circulatory flow paths illustrated in bold in FIG. 30B,the portion of this high-pressure fluid path downstream of reversibleturbomachine system 852, encompassing fluid interconnects 35, 12, 10, 9and ending at HHX system 500 can additionally be considered ahigh-pressure medium-temperature (e.g., HP-MT) fluid path. Similarly,the portion of this high-pressure fluid path downstream of HHX system500, encompassing fluid interconnects 7, 35, and ending at the inlet toreversible turbomachine system 850 can additionally be considered ahigh-pressure high-temperature (e.g., HP-HT) fluid path.

As another example, a low-pressure fluid path is between the CPT system100 turbine system 140 outlet and the CPT compressor system 130 inlet.In FIGS. 3 and 3N, that low-pressure fluid path encompasses fluidinterconnects 19, 14, 2, 5, 11, and 20. With reference to thecirculatory flow paths illustrated in bold in FIG. 3N, the portion ofthis low-pressure fluid path downstream of turbine system 140,encompassing fluid interconnects 19, 14, and ending at CHX system 600can additionally be considered a low-pressure low-temperature (e.g.,LP-LT) fluid path. Similarly, the portion of this low-pressure fluidpath downstream of CHX system 600, encompassing fluid interconnects 2,5, 11, 20, and ending at the inlet to compressor system 130 canadditionally be considered a low-pressure medium-temperature (e.g.,LP-MT) fluid path.

Another low-pressure fluid path is between the GPT system 200 turbinesystem 240 outlet and the compressor system 230 inlet. In FIGS. 3 and3O, that low-pressure fluid path encompasses fluid interconnects 25, 11,5, 4 and 3 (depending on AHX system 700 bypass state), 2, 14, and 26.With reference to the circulatory flow paths illustrated in bold in FIG.3O, the portion of this low-pressure fluid path downstream of turbinesystem 240, encompassing fluid interconnects 25, 11, 5, 4 and 3(depending on AHX system 700 bypass state), 2, and ending at CHX system600 can additionally be considered a low-pressure medium-temperature(e.g., LP-MT) fluid path. Similarly, the portion of this low-pressurefluid path downstream of CHX system 600, encompassing fluidinterconnects 14, 26, and ending at the inlet to compressor system 230can additionally be considered a low-pressure low-temperature (e.g.,LP-LT) fluid path.

As another example, a low-pressure fluid path is between the sharedpowertrain system 800 turbine system 840 outlet and the sharedpowertrain system 800 compressor system 830 inlet. In FIG. 28A, thatlow-pressure fluid path encompasses fluid interconnects 30, 14, 2, 5,11, and 31. In FIG. 28B, that low pressure fluid path encompasses fluidinterconnects 30, 11, 5, 4, 3, 2, 14, and 31. With reference to thecirculatory flow paths illustrated in bold in FIG. 28A, the portion ofthis low-pressure fluid path downstream of turbine system 840,encompassing fluid interconnects 30, 14, and ending at CHX system 600can additionally be considered a low-pressure low-temperature (e.g.,LP-LT) fluid path. Similarly, the portion of this low-pressure fluidpath downstream of CHX system 600, encompassing fluid interconnects 2,5, 11, 31, and ending at the inlet to compressor system 830 canadditionally be considered a low-pressure medium-temperature (e.g.,LP-MT) fluid path. With reference to the circulatory flow pathsillustrated in bold in FIG. 28B, the portion of this low-pressure fluidpath downstream of turbine system 840, encompassing fluid interconnects30, 11, 5, 4, 3, 2, and ending at CHX system 600 can additionally beconsidered a low-pressure medium-temperature (e.g., LP-MT) fluid path.Similarly, the portion of this low-pressure fluid path downstream of CHXsystem 600, encompassing fluid interconnects 14, 31, and ending at theinlet to compressor system 830 can be considered a low-pressurelow-temperature (e.g., LP-LT) fluid path.

As another example, a low-pressure fluid path is between the reversiblepowertrain system 801 reversible turbomachine system 852 outlet, whenreversible turbomachine system 852 is acting as a turbine, and thereversible powertrain system 801 reversible turbomachine system 850inlet, when reversible turbomachine system 850 is acting as acompressor. In FIG. 30A, that low-pressure fluid path encompasses fluidinterconnects 36, 14, 2, 5, 11, and 37. With reference to thecirculatory flow paths illustrated in bold in FIG. 30A, the portion ofthis low-pressure fluid path downstream of reversible turbomachinesystem 852, encompassing fluid interconnects 36, 14, and ending at CHXsystem 600 can additionally be considered a low-pressure low-temperature(e.g., LP-LT) fluid path. Similarly, the portion of this low-pressurefluid path downstream of CHX system 600, encompassing fluidinterconnects 2, 5, 11, 37, and ending at the inlet to reversibleturbomachine system 850 can additionally be considered a low-pressuremedium-temperature (e.g., LP-MT) fluid path.

As another example, a low-pressure fluid path is between the reversiblepowertrain system 801 reversible turbomachine system 850 outlet, whenreversible turbomachine system 850 is acting as a turbine, and thereversible powertrain system 801 reversible turbomachine system 852inlet, when reversible turbomachine system 852 is acting as acompressor. In FIG. 30B, that low-pressure fluid path encompasses thesame fluid interconnects 37, 11, 5, 4, 3, 2, 14, and 36. With referenceto the circulatory flow paths illustrated in bold in FIG. 30B, theportion of this low-pressure fluid path downstream of reversibleturbomachine system 850, encompassing fluid interconnects 37, 11, 5, 4,3, 2, and ending at CHX system 600 can additionally be considered alow-pressure medium-temperature (e.g., LP-MT) fluid path. Similarly, theportion of this low-pressure fluid path downstream of CHX system 600,encompassing fluid interconnects 14, 36, and ending at the inlet toreversible turbomachine system 852 can additionally be considered alow-pressure low-temperature (e.g., LP-LT) fluid path.

Powertrain Isolation in Dual Powertrain PHES Systems

In PHES systems with dual powertrains (e.g., PHES system 1000), valve131 and valve 141 may be closed to isolate the CPT system 100turbomachinery during generation mode 1004. Valve 231 and valve 241 maybe closed to isolate the GPT system 200 turbomachinery during chargemode 1002. As noted above, these isolation valves 131, 141, 231, 241 arepreferably fail-closed valves and preferably they can close quickly tohelp protect the turbomachinery during a trip event.

AHX System Isolation

The AHX system 700 can exhaust excess heat in the working fluid to theenvironment. In some embodiments, excess heat may be rejected from thePHES system (e.g., PHES system 1000, 1003, 1005) via the working fluidloop (e.g., working fluid loops 300, 300C, 300D) only during generation(e.g., mode 1004). Excess heat from inefficiency is generated duringboth charge (e.g. mode 1002) and generation (e.g., mode 1004) due toinefficiencies of the turbomachinery. In an embodiment where excess heatis not rejected during a charge mode (e.g., mode 1002), the excess heataccumulates and results in, for example, a higher CTS medium 690temperature. In an embodiment where excess heat is rejected during ageneration mode (e.g., mode 1004), excess heat from charge modeinefficiency and generation mode inefficiency can be removed from theworking fluid loop through the AHX system 700.

Consequently, in a preferred embodiment, it is desirable to provide amode-switchable working fluid heat dissipation system that can beactivated during generation mode 1004 and bypassed during charge mode1002, or vice versa in another embodiment. In a working fluid loop(e.g., working fluid loops 300, 300C, 300D), as depicted for example inFIGS. 3, 3N, 30, 28, 28A, 28B, 30, 30A, 30B, an arrangement of valvesallow AHX system 700 to be activated or bypassed depending on the mode(e.g., modes 1002, 1004, or other modes, transitions, or state asfurther described with respect to, for example, FIGS. 10 and/or 11). Aset of three valves, 323, 324, 325 direct working fluid flow through theAHX system 700 during generation mode, as illustrated in FIGS. 3O, 28B,30B, and direct working fluid to bypass the AHX system 700 during chargemode, as illustrated in FIG. 3N, 28A, 30A. To direct working fluid flowthrough the AHX system 700, valve 323 may be closed and valves 324 and325 open. Conversely, to bypass AHX system 700, valve 323 may be openedand valves 324 and/or 325 may be closed. FIGS. 31 and 3J and theircorresponding disclosure further illustrate the bypass and active statesof AHX system 700. Alternatively, in another embodiment, valve 325 maybe omitted and valves 323 and 324 are used to provide a mode-switchableheat dissipation system, as further illustrated and described herein andwith respect to FIGS. 3K and 3L.

Inventory Control System

Inventory control refers to control of the mass, and correspondingpressures, of working fluid in the high-pressure and low-pressure sidesof a working fluid loop (e.g., working fluid loops 300, 300C, 300D),which can be controlled to affect, for example, power generation andcharge characteristics of a PHES system (e.g., PHES system 1000, 1003,1005). Control of working fluid inventory inside the working fluid loopcan be accomplished with components illustrated in FIGS. 3, 28, 30, andadditionally illustrated as ICS 300B in FIG. 3M, which can beimplemented in any of the PHES system embodiments herein. One or morecontrollers, such as illustrated in FIG. 24A, may participate in and/ordirect the control. Using inventory control, power of the PHES system ispreferably modulated by adjusting working fluid pressure in thelow-pressure side of the working fluid loop.

In one example of inventory control, a high-pressure tank system and alow-pressure tank system and associated valves are used to control theamount of working fluid circulating in a working fluid loop (e.g.,working fluid loops 300, 300C, 300D). High-pressure tank system 320,which may include one or more fluid tanks for holding working fluid, canbe connected to a high-pressure working fluid path via valve 321 and toa low-pressure working fluid path via valve 322. Low-pressure tanksystem 310, which may include one or more fluid tanks, can be connectedto a high-pressure working fluid path via valve 311 and to alow-pressure working fluid path via valve 312. The four valves, 311,312, 321, and 322, may be used to control the direction of working fluidflow between the tank systems 310, 320 and low-pressure or high-pressurefluid paths in the working fluid loop, effectively allowing the additionor removal of working fluid circulating through the working fluid loop.

ICS 300B further includes a make-up working fluid compressor 303 thatcan add working fluid to the working fluid loop (e.g., working fluidloops 300, 300C, 300D). The working fluid loop operates as a closedloop; however, working fluid may be lost over time or intentionally lostdue to operational decisions or hardware protection-related operations,such as venting of working fluid in overpressure conditions. Workingfluid can be added to the working fluid loop by adding outside workingfluid through a working fluid filter 301. To get the outside workingfluid into the high-pressure tank system 320, the working fluidcompressor 303 is used to pressurize outside working fluid to a pressuregreater than the high-pressure tank system 320 (or greater than at leastone tank in the high-pressure tank system 320). In an embodiment wherethe working fluid is air, ambient air may be brought in through thefilter 301 and pressurized with the compressor 303. In otherembodiments, an outside working fluid make-up reservoir (not shown) maysupply working fluid to the filter 301 or the compressor 303.

In another example of inventory control, after a normal shutdown or atrip event in a PHES system (e.g., PHES system 1000, 1003, 1005),pressure in a working fluid loop (e.g., working fluid loops 300, 300C,300D) is preferably brought to a lower pressure before a powertrainsystem (e.g., CPT system 100, GPT system, 200, shared powertrain 800,reversible powertrain 801) is started. This is beneficial because ifhigh pressure in high-pressure fluid paths of the working fluid loop isnot lowered prior to some mode transitions, the resulting settle-outpressure throughout the working fluid loop would require thatlow-pressure fluid paths in the working fluid loop be designed to workwith higher pressures than typical operating pressures in thelow-pressure fluid paths during charge or generation modes. Thus, ifworking fluid can be removed from the working fluid loop duringspin-down (e.g., transition to hot turning mode 1006 and/or slow rollingstate), lower-pressure piping and components can be used in thelow-pressure fluid paths of the working fluid loop, thus allowingreduced capital investment in the PHES system design. Therefore, it isdesirable to bring the circulating working fluid mass down so that thesettle-out pressure in the working fluid loop is no more than thetypical low-side pressure in the working fluid loop.

In one example, working fluid loop (e.g., working fluid loops 300, 300C,300D) pressure reduction can be accomplished by using the working fluidcompressor 303 to take working fluid from a high-pressure fluid path viavalve 305, or to take working fluid from a low-pressure fluid path viavalve 304, preferably one at a time, and push the working fluid into thehigh-pressure tank system 320. Additionally or alternatively, valves 311or 318 can be used to slowly or quickly bleed down pressure from ahigh-pressure fluid path into the lower pressure tank system 310.

In another example, ICS 300B includes at least one evacuation valve 308controllable to vent working fluid from the low-pressure side of aworking fluid loop (e.g., working fluid loops 300, 300C, 300D), as wellas pressure relief devices throughout the working fluid loop to provideprotection from overpressure.

In another example, ICS 300B includes at least one evacuation valve 314controllable to vent working fluid from the high-pressure side of aworking fluid loop (e.g., working fluid loops 300, 300C, 300D)0, as wellas pressure relief devices throughout the working fluid loop to provideprotection from overpressure.

Powertrain Bypass/Recirculation Loops

For each turbomachinery powertrain (e.g., CPT system 100, GPT system200, shared powertrain system 800, reversible powertrain system 801),there are working fluid recirculation and bypass loops. A recirculationloop may be characterized as a switchable closed-loop working fluid paththat allows recirculation of working fluid from the outlet of acomponent back to the inlet of the component. For example, arecirculation loop can be used around a compressor system during hotturning. In this example, working fluid is routed from the compressorsystem outlet back to the compressor inlet instead of through the mainheat exchangers, allowing the compressor system to gradually cool downafter the compressor system transitions from high flow rate operation(e.g. charge mode 1002 or generation mode 1004) to low flow rateoperation (e.g., hot turning mode 1006).

A bypass loop may be characterized as a switchable closed-loop workingfluid path that routes working fluid around one or more components inthe main working fluid loop (e.g., working fluid loops 300, 300C, 300D).For example, during transition from a generation mode 1004 to a tripmode 1012, a bypass loop may be activated during that high flow rateperiod. The bypass loop could route high flow rate working fluid from ageneration compressor system outlet away from the heat exchangers and toa generation turbine system inlet. A bypass loop can be beneficialduring trip events (e.g., mode 1012) when surging of the turbomachineryis a risk, and also during turbomachinery startup when it is desirableto reduce startup power.

Valve 119, which is normally closed, can open a preferably high flowrate bypass loop around a compressor system (e.g., compressor system130, compressor system 830, reversible turbomachine system 850 acting asa compressor). This is beneficial, for example, to prevent surge in thecompressor system during a trip event from charge mode.

Valve 132, which is normally closed, can open a recirculation looparound a compressor system (e.g., compressor system 130, compressorsystem 830, reversible turbomachine system 850 acting as a compressor).The valve 132 recirculation loop can be activated to allow circulationand also cooling of the working fluid through the heat exchanger 132.The valve 132 recirculation loop may have lower flow rate capabilitythan the valve 119 recirculation loop. The valve 132 recirculation loopcan be beneficial, for example, during a hot turning mode.

For the CPT system 100, valve 142, which is normally closed, can open arecirculation loop around the charge turbine system 140 to allowrecirculation during, for example, hot turning mode for the CPT system100. As previously noted, fan 142F may assist with working fluid flow inthis recirculation loop. For the reversible powertrain system 801, valve142, which is normally closed, can open a recirculation loop around thereversible turbomachine 852 acting as a turbine to allow recirculationduring, for example, a hot turning mode. Fan 142F may assist withworking fluid flow in this recirculation loop. For the shared powertrainsystem 800, valve 842, which is normally closed and functions similarlyto valve 142, can open a recirculation loop around the turbine system840 to allow recirculation during, for example, a hot turning mode.Similarly, fan 842F may assist with working fluid flow in thisrecirculation loop.

Valve 229, which is normally closed, can open a preferably high flowrate bypass fluid path from the outlet of a generation compressor system(e.g., compressor system 230, compressor system 830 in generation mode,reversible turbomachine system 852 acting as a compressor) to the outletfluid path of a generation turbine system (e.g., turbine system 240,turbine system 840, reversible turbomachine system 850 acting as aturbine) to reduce start-up power at the powertrain system (e.g., GPTsystem 200, shared powertrain 800, reversible powertrain 801). Routingworking fluid through the valve 229 bypass loop reduces the magnitude ofpower for each of the generation compressor system and the generationturbine system, and thus reduces the net power magnitude of thepowertrain system. In effect, the valve 229 bypass loop creates alimited starving effect in the powertrain system. The effect on thegeneration turbine system is greater than the effect on the generationcompressor system. Consequently, opening the valve 229 bypass loop cankeep generation turbine system power production less than generationcompressor system power draw. Because that ensures a net electricalpower input need, a generator system or motor/generator system (e.g.,generator system 210 acting as a motor, motor/generator system 810acting as a motor) must still act as a motor during the duration ofspin-up. Beneficially, this maintains VFD control of the spin-upprocess. As another benefit, opening the valve 229 bypass loop canprovide surge protection during a trip event.

Valve 232, which is normally closed, can open a recirculation looparound a generation compressor system (e.g., compressor system 240,reversible turbomachine system 852 acting as a compressor) to provideworking fluid circulation through the generation compressor systemduring, for example, hot turning mode. In a shared powertrain workingfluid loop, such as working fluid loop 300C in FIG. 28B, valve 132 maybe used similarly or the same as valve 232, as further described herein.

Valve 242, which is normally closed, can open a recirculation looparound a generation mode turbine system (e.g., turbine system 240,reversible turbomachine system 850 acting as a turbine). Thisrecirculation loop can be activated to allow circulation and alsocooling of the working fluid recirculating through the heat exchanger242H, thereby cooling the generation turbine system 240. This isbeneficial during, for example, hot turning mode.

In a shared powertrain PHES system, (e.g., PHES system 1003), valve 842and heat exchanger 842H can act similarly to, or the same as, valve 242and heat exchanger 242H, respectively, when the PHES system is in ageneration mode. Valve 842 regulates a recirculation fluid path around aportion of the generation mode turbine system (e.g., turbine system 840,see FIG. 34B) that can be opened, for example, to recirculate workingfluid through the turbine system during, for example, cooldown (e.g.during slow rolling) or after a mode switch. Valve 842 may exhibit slowresponse time and preferably fails open. A benefit of valve 842 failingopen is that if valve 842 fails, by failing open it allows for cooldownspinning of the powertrain system (e.g., shared powertrain system 800)after shutdown of the powertrain system. Cooldown spinning can preventbowing of rotating components in the turbomachinery. Another benefit ofvalve 842 failing open is that, when failed open, the powertrain systemcan continue to function during generation (e.g., mode 1004) or slowturning (e.g., mode 1006), albeit with decreased efficiency duringgeneration due to open valve 842 creating a bleed path for the workingfluid.

Valve 222, which is normally closed, can be opened to provide to providea working fluid bypass path around the high-pressure side of RHX system400 and HHX system 500 for a generation powertrain system (e.g., GPTsystem 200, shared powertrain system 800 in generation mode, reversiblepowertrain system 801 in generation mode). This is further describedabove with respect to valve 222 and valve 401.

Other recirculation and bypass valves may be implemented in a PHESsystem (e.g., PHES system 1000, 1003, 1005) to provide functionality insurge prevention, overspeed prevention, overpressure prevention, startupload reduction, and low thermal ramping of components.

F. Hot-Side Thermal Storage Subsystem

FIG. 4 is a schematic fluid path diagram of a hot-side thermal storagesystem which may be implemented in a PHES system, such as PHES systems1000, 1003, 1005 according to an example embodiment. Other embodimentsof an HTS system operable in PHES systems disclosed herein are possibleas well. FIG. 4 provides additional detail concerning an HTS system 501embodiment than is shown in the top-level schematics of FIGS. 2, 27, 29.In general terms, HTS system 501 includes tanks for HTS medium, HTSmedium fluid paths, pumps, valves, and heaters. The HTS system 501 iscapable of transporting HTS medium 590 back and forth between the two(or more) storage tanks to allow charging of the warm HTS medium 590(i.e., adding thermal energy) or discharging of the HTS medium 590(i.e., extracting thermal energy). The heaters are available to ensurethat the HTS medium 590 remains in liquid phase for anticipatedoperational conditions in PHES systems 1000, 1003, 1005.

An HTS system, such as the embodiment of HTS system 501 illustrated inFIG. 4, can serve numerous roles within a PHES system (e.g., PHES system1000, 1003, 1005). An HTS system may ensure that HTS medium 590 remainsin liquid phase during all modes of operation of the PHES system. An HTSsystem may deliver HTS medium 590 flow to the HHX system 500 to storeheat in the HTS medium 590 during charge mode operation of the PHESsystem (e.g. mode 1002). An HTS system may deliver HTS medium 590 flowto the HHX system 500 to provide heat from the HTS medium 590 to theworking fluid during generation mode operation of the PHES system (e.g.,mode 1004). An HTS system may drain HTS medium 590 from the PHES systeminto at least one storage tank. An HTS system may vent entrapped gas inHTS medium 590 fluid paths. An HTS system may protect fluid paths andcomponents from over pressurization. An HTS system may isolate itselffrom the other PHES system subsystems when the HHX system 500 isdisconnected for service, or for thermal rebalancing of the HTS systemand/or PHES system. An HTS system may maintain pressure of the HTSmedium 590 in the HHX system 500 to be less than that of the workingfluid pressure in the working fluid loop 300 at HHX system 500, forexample, to prevent leakage of HTS medium into the working fluid loop(e.g., working fluid loops 300, 300C, 300D).

In the embodiment of an HTS system shown in FIG. 4, the HTS system 501includes two tanks: a warm HTS tank 510 for storing warm HTS medium 590(e.g., at approximately 270° C.) and a hot HTS tank 520 for storing hotHTS medium 590 (e.g., at approximately 560° C.). In other embodiments,more than one tank may be used to increase the storage capacity of thewarm HTS storage 591 and/or the hot HTS storage 592. Each HTS tank 510,520 has a pump, an immersion heater, and sensors.

In HTS system 501, warm HTS pump 530 circulates HTS medium 590 from warmHTS tank 510, through fluid interconnect 8, through HHX system 500,through fluid interconnect 6, and to the hot HTS tank 520 during PHEScharging mode (e.g., mode 1002), where the HTS medium 590 is absorbingheat from the working fluid side of the HHX system 500. Hot HTS pump 540circulates HTS medium 590 from hot HTS tank 520, through fluidinterconnect 6, through HHX system 500, through fluid interconnect 8,and to the warm HTS tank 510 during PHES system generation mode (e.g.,mode 1004), where the HTS medium 590 is providing heat to the workingfluid side of the HHX system 500.

In HTS system 501, valves in HTS system 501 can be actuated to bypassthe HHX system 500 as necessary in order to isolate HTS tanks 510, 520from the rest of PHES system (e.g., PHES system 1000, 1003, 1005) and/orto facilitate thermal balancing of the HTS loop and/or PHES system. Theability to facilitate balancing can be beneficial, for example, tomaintain thermal balance between PHES system charge and generationcycles. It is desirable that the mass of HTS medium 590 transferred fromwarm HTS tank 510 to hot HTS tank 520 during charge (e.g. charge mode1002) is later transferred back from hot HTS tank 520 to warm HTS tank510 during generation (e.g., generation mode 1004), and vice versa.However, disturbances to the HTS medium flow rate during charge andgeneration cycles, resulting from, for example, uneven heat loss acrossthe PHES system, may result in unequal masses of HTS medium 590transferred between the cycles. If that occurs, direct transfer of HTSmedium 590 from warm HTS tank 510 to hot HTS tank 520, or vice versa,may be used to re-balance HTS medium 590 masses at the beginning or endof a charge or generation cycle.

In HTS system 501, valves can be actuated to drain HTS medium 590 influid paths, including HHX system 500, into one or more tanks asnecessary.

In HTS system 501, heat traces can be used throughout the fluid paths toavoid formation of solid HTS medium 590 during filling of the HTS system501 and/or during hot turning mode (e.g., mode 1006) or hot standby mode(e.g., mode 1008) where there may be no significant flow of HTS medium590 through fluid paths.

The following paragraphs describe components of the HTS system 501:

Warm HTS tank 510 is a tank for storing warm HTS medium 590. In otherembodiments, there may be additional warm HTS tanks.

Sensors 510S, 520S are monitoring and reporting devices that can providetemperature and/or fluid level data for HTS medium 590 in tanks 510,520, respectively, to one or more control systems controlling and/ormonitoring conditions in the PHES system (e.g., PHES system 1000, 1003,1005).

Valve 511 is a bypass valve that provides a flow path for HTS medium 590to go directly into the warm tank 510, bypassing the pump 530 when valve557 is closed.

Heater 512 provides heat to HTS medium 590 in warm HTS tank 510, forexample, to ensure it stays in liquid form.

Hot HTS tank 520 is a tank for storing hot HTS medium 590. In otherembodiments, there may be additional hot HTS tanks.

Valve 521 is a bypass valve that provides a flow path for HTS medium 590to go directly into the hot tank 520, bypassing the pump 540 when valve558 is closed.

Heater 522 provides heat HTS medium 590 in hot tank 520, for example, toensure it stays in liquid form.

Breather device 529 allows ambient air in and out of the tank head spaceas the HTS medium 590 expands and contracts with temperature.

Warm HTS pump 530 delivers HTS medium 590 from warm HTS tank 510 to hotHTS tank 520 via HHX system 500 during charge mode operation. Dependingon valve state, pump 530 can alternatively or additionally deliver HTSmedium 590 to hot HTS tank 520 via bypass valve 551, bypassing HHXsystem 500, for balancing purposes. In other embodiments, there may beadditional warm HTS pumps.

Hot HTS pump 540 delivers HTS medium 590 from hot HTS tank 520 to warmHTS tank 510 via HHX system 500 during generation mode operation.Depending on valve state, pump 540 can alternatively or additionallydeliver HTS medium 590 to warm HTS tank 510 via valve 551, bypassing HHXsystem 500, for balancing purposes. In other embodiments, there may beadditional hot HTS pumps.

Valve 551 is an HHX system 500 bypass valve that provides a fluid flowpath allowing HTS medium 590 to travel between HTS tanks 510, 520 whilebypassing HHX system 500.

Sensors 5515, 552S are monitoring and reporting devices that can providetemperature, flow, and/or pressure data to one or more control systemscontrolling and/or monitoring conditions in the PHES system (e.g., PHESsystem 1000, 1003, 1005).

Valve 552 is a drain valve that provides a fluid flow path for drainingof HTS medium 590 into or out of warm tank 510.

Valve 553 is a drain valve that provides a fluid flow path for drainingof HTS medium 590 into or out of hot tank 520.

Valve 554 is a check valve that works as a gas release valve to allowaccumulated gas in the HTS system 501 to migrate to a tank cover gasspace in either or both tanks 510, 520.

Valve 555 is an HHX system 500 isolation valve that restricts HTS medium590 flow between the HHX system 500 and HTS system 501 throughinterconnect 8.

Valve 556 is an HHX system 500 isolation valve that restricts HTS medium590 flow between the HHX system 500 and HTS system 501 throughinterconnect 6.

Valves 552, 553, 555, and 556 can all be closed to isolate HHX system500 from HTS medium 590 in the HTS system 501.

Valve 557 is a warm CTS pump 530 outlet valve that can be opened toallow CTS medium 590 flow from warm CTS pump 530 or closed to preventflow into the outlet of hot CTS pump 530.

Valve 558 is a hot CTS pump 540 outlet valve that can be opened to allowCTS medium 590 flow from hot CTS pump 540 or closed to prevent flow intothe outlet of hot CTS pump 540.

Heat trace 560 can be activated to maintain fluid paths and/or othermetal mass at temperatures sufficient to keep the HTS medium 590 inliquid phase, and/or at desired setpoint temperatures during variousmodes and/or states of a PHES system (e.g., PHES system 1000, 1003,1005) in order to reduce thermal gradients on sensitive components,and/or to reduce transition time between the PHES system modes andstates. Beneficially, heat trace 560 can reduce thermal ramp rates,which benefits component longevity, and allows for faster startup times.Heat trace 560 is illustrated as near fluid interconnect 8 and on thewarm tank 510 side of HTS system 501. However, heat trace 560 can belocated at other locations within HTS system 501 in order to accomplishits functions. Additionally or alternatively, heat trace 560 can includeheat traces at multiple locations within HTS system 501 in order toaccomplish its functions.

Operation of HTS System

During operation of a PHES system (e.g., PHES system 1000, 1003, 1005)in a generation mode (e.g. mode 1004), the HTS system 501 is configuredsuch that hot HTS medium 590 is delivered from hot HTS tank 520 to warmHTS tank 510 via HHX system 500 at a fixed and/or controllable rateusing pump 540. During generation, heat from the hot HTS medium 590 istransferred to the working fluid via the HHX system 500. The ratedgeneration flow of HTS medium 590 at a given PHES system power may be afunction of the generation flow of CTS medium 690 to maintain inventorybalance.

During operation of a PHES system (e.g., PHES system 1000, 1003, 1005)in a charge mode (e.g. mode 1002), the HTS system 501 is configured suchthat warm HTS medium 590 can be delivered from warm HTS tank 510 to hotHTS tank 520 via HHX system 500 at a fixed or controllable rate usingthe pump 530. During charge, the warm HTS medium 590 absorbs heat fromthe hot working fluid via the HHX system 500. The rated charge flow ofHTS medium 590 at a given PHES system power may be a function of thecharge flow of CTS medium 690 to maintain inventory balance.

Under some PHES system (e.g., PHES system 1000, 1003, 1005) modes, suchas long-term Cold Dry Standby, the HTS medium 590 in the hot-side loop(e.g., HTS system 501, HHX system 500, and intermediate fluid paths)needs to be drained to the HTS tanks 510 and/or 520. In this scenario,preferably the heater 512 in the warm tank 510 is used to ensure HTSmedium 590 remain in liquid form. Preferably, for example, the hot HTSpump 540 can be used to transfer hot HTS medium 590 from the hot HTStank 520 to the warm HTS tank 510 via the HHX system 500 bypass line(e.g., via valve 551) and valve 511. Alternatively, warm HTS pump 530can be used to transfer warm HTS medium 590 from the warm HTS tank 510to the hot HTS tank 520 via the HHX system 500 bypass line (e.g., viavalve 551) and valve 521. HTS 590 medium remaining in hot HTS tank 520may also be kept in a liquid state with heater 522.

Under certain operating modes, HHX system 500 can be bypassed by closingvalves 552, 553, 555, and 556, opening valve 551, and using pump 530 or540 to cause flow of HTS medium 590 between HTS tanks 510 and 520 Forexample, HHX system 500 can be bypassed to balance the thermal energycontent either between the HTS tanks 510, 520 individually and/or tobalance total thermal energy between HTS system 501 and CTS system 601.

G. Cold-Side Thermal Storage Subsystem

FIG. 5 is a schematic fluid path diagram of a cold-side thermal storagesystem which may be implemented in a PHES system, such as PHES systems1000, 1003, 1005 according to an example embodiment. Other embodimentsof a CTS system operable in PHES systems disclosed herein are possibleas well. FIG. 5 provides additional detail concerning a CTS system 601embodiment than is shown in the top-level schematic of FIGS. 2, 27, 29.In general terms, CTS system 601 includes tanks for CTS medium, CTSmedium fluid paths, pumps, valves, and inert gas supply. The CTS system601 is capable of transporting CTS medium 690 back and forth between thetwo (or more) storage tanks to allow charging of the CTS medium 690(i.e., removing thermal energy) or discharging of the CTS medium 690(i.e., adding thermal energy). During PHES system charge mode operation,the CTS medium 690 deposits heat to working fluid inside the CHX system600. During PHES system generation mode operation, the CTS medium 690absorbs heat from the working fluid inside the CHX system 600.

A CTS system, such as CTS system 601 illustrated in FIG. 5, can servenumerous roles within a PHES system, such as PHES systems 1000, 1003,1005. A CTS system may deliver CTS medium 690 flow to the CHX system 600to provide heat during charge mode operation of a PHES system 1000(e.g., mode 1002). A CTS system may deliver CTS medium 690 flow to theCHX system 600 to absorb heat during generation mode operation of thePHES system (e.g., mode 1004). A CTS system may drain CTS medium 690into at least one storage tank. A CTS system may vent entrapped gas inCTS medium 690 fluid paths. A CTS system may protect fluid paths andcomponents from over pressurization. A CTS system 601 may isolate itselffrom other PHES system subsystems when the CHX system 600 isdisconnected for service, or for thermal rebalancing. A CTS system mayisolate the CTS medium 690 from ambient via an inert gas blanket. A CTSsystem may maintain pressure of the CTS medium 690 in the CHX system 600to be less than that of the working fluid pressure in the a workingfluid loop (e.g., working fluid loops 300, 300C, 300D) at CHX system600, for example, to prevent leakage of CTS medium into the workingfluid loop. A CTS system 601 may monitor CTS medium 690 health duringoperation.

In the embodiment of a CTS system shown in FIG. 5, the CTS system 601includes two tanks: a warm CTS tank 610 for storing warm CTS medium 690(e.g., at approximately 30° C.) and a cold CTS tank 620 for storing coldCTS medium 690 (e.g., at approximately −60° C.). In other embodiments,more than one CTS tank may be used to increase the storage capacity ofthe warm CTS storage 691 and/or the cold CTS storage 692. In CTS system601, each CTS storage 691, 692 has a pump system 639, 649, respectively.

In CTS system 601, warm pump 630 circulates CTS medium 690 from warm CTStank 610, through fluid interconnect 1, through CHX system 600, throughfluid interconnect 13, and to the cold CTS tank 620 during a PHEScharging mode (e.g., mode 1002), where the CTS medium 690 is providingheat to the working fluid side of the CHX system 600. The cold pump 640circulates CTS medium 690 from cold CTS tank 620, through fluidinterconnect 13, through CHX system 600, through fluid interconnect 1,and to the warm CTS tank 610 during a PHES system generation mode (e.g.,mode 1004), where the CTS medium 690 is absorbing heat from the workingfluid side of the CHX system 600.

Valves in CTS system 601 can be actuated to bypass the CHX system 600 asnecessary in order to isolate CTS storage 691, 692 from the rest of aPHES system (e.g., PHES system 1000, 1003, 1005) and/or to facilitatebalancing of the CTS loop. The ability to facilitate balancing can bebeneficial, for example, to maintain thermal balance between PHES systemcharge and generation cycles. It is desirable that the mass of CTSmedium 690 transferred from warm CTS tank 610 to cold CTS tank 620during charge (e.g. charge mode 1002) is later transferred back fromcold CTS tank 620 to warm CTS tank 610 during generation (e.g.,generation mode 1004). However, disturbances to the CTS flow rate duringcharge and generation cycles, resulting from, for example uneven heatloss across the PHES system, may result in unequal masses of CTS medium690 transferred between the cycles. If that occurs, direct transfer ofCTS medium 690 from warm CTS tank 610 to cold CTS tank 620, or viceversa, may be used to re-balance CTS medium 690 masses at the beginningor end of a charge or generation cycle.

In CTS system 601, valves can be actuated to drain CTS medium 690 influid paths, including CHX system 600, into one or more tanks asnecessary.

In an embodiment of CTS system 601, one, or both of, CTS pumps 630, 640are capable of bidirectional flow. Beneficially, reverse pumping can beused to provide active pressure reduction in the CTS loop, which can beemployed to keep CTS medium 690 pressure in CHX system 600 below workingfluid pressure in CHX system 600. This working fluid positive pressurecondition (with respect to CTS medium 690) beneficially prevents any CTSmedium from leaking into working fluid loop (e.g., working fluid loops300, 300C, 300D), for example, through cracked heat exchanger cores.

The following paragraphs describe components of the CTS system 601:

Valve 602 is a CHX system 600 isolation valve that restricts CTS medium690 flow between the CHX system 600 and CTS system 601 throughinterconnect 13.

Valve 603 is a CHX system 600 isolation valve that restricts CTS medium690 flow between the CHX system 600 and CTS system 601 throughinterconnect 1.

Valves 602, 603 can both be closed to isolate the CHX system 600 fromCTS medium 690 in the CTS system 601.

Valve 605 is a CHX system 600 bypass valve that provides a fluid flowpath allowing CTS medium 690 to travel between CTS tanks 610, 620 whilebypassing CHX system 600.

Warm CTS tank 610 is a tank for storing warm CTS medium 690.

Sensors 610S, 620S are monitoring and reporting devices that can providetemperature and/or fluid level data for HTS medium 690 in tanks 610,620, respectively, to one or more control systems controlling and/ormonitoring conditions in a PHES system (e.g., PHES system 1000, 1003,1005).

Valve 611 is an isolation valve that isolates warm CTS tank 610 from theCTS loop.

Pressure relief device 619 protects CTS tanks 610, 620 from overpressurization via a gas fluid path between the headspace of CTS tanks610, 620.

Cold CTS tank 620 is a tank for storing cold CTS medium 690.

Valve 621 is an isolation valve that isolates cold CTS tank 620 from theCTS loop.

Inert gas reservoir 622 is a storage reservoir for an inert gas (e.g.,nitrogen) useable as a cover gas to blanket CTS medium 690 in tanks 610,620.

Valve 623 is an inert gas fluid path valve that can control a flow ofinert gas from inert gas reservoir 622 to the headspace of CTS tanks620, 621 which are connected via a gas fluid path. Valve 623 can be usedto regulate the pressure of an inert gas blanket within the CTS tanks610, 620.

Valve 624 is an inert gas purge valve that can control a flow ofpressurized inert gas into the cold-side loop CTS medium 690 fluid pathsto purge those fluid paths of CTS medium 690.

Warm CTS pump 630 delivers CTS medium 690 from warm CTS tank 610 to coldCTS tank 620 via CHX system 600 during charge mode operation (e.g., mode1002) of a PHES system (e.g., PHES system 1000, 1003, 1005). Dependingon valve states, pump 630 can alternatively or additionally deliver CTSmedium 690 to cold CTS tank 620 via valve 605, bypassing CHX system 600,for balancing purposes. In other embodiments, there may be additionalwarm CTS pumps.

Valve 631 is a warm pump 630 isolation valve that, when closed, canisolate pump 630, for example during a PHES system (e.g., mode 1002)generation mode when CTS medium 690 is flowing from cold CTS tank 620 towarm CTS tank 610. In an embodiment where pump 630 is bidirectional andoperating in reverse, valve 631 may be open during generation mode toallow active pressure reduction in the CTS loop.

Valve 632 is a warm CTS pump 630 bypass valve that provides a flow patharound pump 630 during, for example, generation mode operation (e.g.,mode 1004) of a PHES system (e.g., PHES system 1000, 1003, 1005) orbalancing of CTS medium 690 in CTS system 601.

Valve 633 is a warm pump 630 isolation valve that, when closed alongwith warm pump outlet valve 631, allows for servicing of warm pump 630when the pump is not in use, for example during a PHES system (e.g.,PHES system 1000, 1003, 1005) generation mode (e.g., mode 1004) when CTSmedium 690 is flowing to warm tank 610 through pump 630 bypass valve632.

Warm CTS pump system 639 and cold CTS pump system 649 illustraterespective CTS medium 690 pumping systems for warm CTS storage 691 andcold CTS storage 692, respectively.

Cold pump 640 delivers CTS medium 690 from cold CTS tank 620 to warm CTStank 610 via CHX system 600 during generation mode (e.g., mode 1004)operation of a PHES system (e.g., mode 1004). Depending on valve state,pump 640 can alternatively or additionally deliver CTS medium 690 towarm CTS tank 620 via valve 605, bypassing CHX system 600, for balancingpurposes. In other embodiments, there may be additional cold CTS pumps.

Valve 641 is a cold pump 640 isolation valve that, when closed, canisolate pump 640, for example during PHES system (e.g., mode 1004)charge mode when CTS medium 690 is flowing from warm CTS tank 610 tocold CTS tank 620. In an embodiment where pump 640 is bidirectional andoperating in reverse, valve 641 may be open during generation mode toallow active pressure reduction in the CTS loop.

Valve 642 is a cold CTS pump 640 bypass valve that provides a flow patharound pump 640 during, for example, charge mode (e.g., mode 1002)operation of the PHES system (e.g., PHES system 1000, 1003, 1005) orbalancing of CTS medium 690 in CTS system 601.

Valve 643 is a cold pump 640 isolation valve that, when closed alongwith cold pump outlet valve 641, allows for servicing of cold pump 640when the pump is not in use, for example during a PHES system (e.g.,PHES system 1000, 1003, 1005) charge mode when CTS medium 690 may beflowing to cold tank 620 through pump 640 bypass valve 642.

Sensors 661S, 662S, 663S, 664S, 665S, 666S, 667S, 668S are monitoringand reporting devices that can provide temperature, flow, and/orpressure data to one or more control systems controlling and/ormonitoring conditions in a PHES system (e.g., PHES system 1000, 1003,1005).

Valve 682 is a check-style vent valve that allows entrapped CTS medium690 gas in CTS loop fluid paths (e.g., CTS system 601 and CHX system600) to be vented to a cover gas region of the CTS tanks 610, 620, butprevents gas or fluid from the CTS tanks from flowing back towards CHXsystem 600.

Operation of CTS System

During a PHES system (e.g., PHES system 1000, 1003, 1005) charge mode(e.g., mode 1002), warm pump 630 delivers warm CTS medium 690 at a fixedor controllable rate from warm CTS tank 610 to cold CTS tank 620 via CHXsystem 600. During charge, heat from the warm CTS medium 690 istransferred to the working fluid via the CHX system 600. The ratedcharge flow of CTS medium 690 at a given PHES system power may be afunction of the charge flow of HTS medium 590 to maintain inventorybalance. The cold CTS pump 640 can be used to reduce pressure at the CHXsystem 600 by pulling CTS medium 690 from there.

During PHES system (e.g., PHES system 1000, 1003, 1005) generation mode(e.g., mode 1004), the cold pump 640 delivers cold CTS medium 690 at afixed or controllable rate from the cold CTS tank 620 to the warm CTStank 610 through CHX system 600. The rated generation flow of CTS medium690 at a given PHES system power may be a function of the generationflow of HTS medium 590 to maintain inventory balance. The warm coolantpump 630 can be used to reduce pressure at the CHX system 600 by pullingCTS medium 690 from there.

Under some PHES system (e.g., PHES system 1000, 1003, 1005) modes, suchas long-term Cold Dry Standby, the CTS medium 690 in the cold-side loop(e.g., CTS system 601, CHX system 600, and intermediate fluid paths)needs to be drained to the CTS tanks 610 and/or 620. For example, coldpump 640 can be used to transfer cold CTS medium 690 in the cold tank620 to the warm tank 610 via a fluid path through bypass valve 605.

Under certain operating modes, CHX system 600 can be bypassed by closingvalves 602, 603 and opening valve 605, and using pumps 630 and/or 640 tocause flow of CTS medium 690 between CTS tanks 610 and 620. For example,CHX system 600 can be bypassed to balance the thermal energy contenteither between CTS tanks 610, 620 individually and/or to balance totalthermal energy between CTS system 601 and HTS system 501.

III. Illustrative PHES System—Shared Powertrain

FIG. 27 is a top-level schematic diagram of a PHES system 1003 with ashared powertrain, according to an example embodiment, in which PHESsystem and subsystem embodiments herein may be implemented. As atop-level schematic, the example embodiment PHES system 1003 in FIG. 27illustrates major subsystems and select components, but not allcomponents. Additional components are further illustrated with respectto additional figures detailing various subsystems. Additionally oralternatively, in other embodiments, additional components and/orsubsystems may be included, and/or components and/or subsystems may notbe included. FIG. 27 further illustrates select components andsubsystems that work together in the PHES system 1003. FIG. 27schematically shows how the select components and subsystems connect,how they are grouped into major subsystems, and select interconnectsbetween them.

PHES system 1003 utilizes components, fluids, controls, functions,operations, capabilities, systems, subsystems, configurations,arrangements, modes, states, benefits, and advantages described withrespect to PHES system 1000, except that PHES system 1003 includes ashared powertrain (“SPT”) system 800 in lieu of the dual powertrains,CPT system 100 and GPT system 200, and a working fluid loop 300C in lieuof working fluid loop 300.

In FIG. 27, illustrated exemplary components in SPT system 800 includemotor/generator system 810, gearbox system 820, compressor system 830,and turbine system 840. Motor/generator system 810 may include one ormore motors, generators, and/or motor/generators. Gearbox system 820 mayinclude one or more gearboxes connecting one or more components of themotor/generator system 810 to one or more components of the compressorsystem 830 and/or turbine system 840. Compressor system 830 may includeone or more compressors. Turbine system 840 may include one or moreturbines.

Depending on operational mode, state, and embodiment configuration, SPTsystem 800 may connect to other components and subsystems of PHES system1003 through various interconnects, including electrical interconnect 32and fluid interconnects 28, 28A, 29, 29A, 30, 30A, 31, 31A. Fluidinterconnect pairs 28 and 28A, 29 and 29A, 30 and 30A, 31 and 31A, mayshare common connections between the pairs or may be separate asillustrated. SPT system 800 may include more or fewer interconnects thanshown in FIG. 27. The SPT system 800 can accept electrical power in atelectrical interconnect 32 and convert the electrical energy to workingfluid flows through one or more of its fluid interconnects.Additionally, SPT system 800 can output electrical power throughelectrical interconnect 32 as a result of energy generated by SPT system800.

Power/signal path 902 connects electrical interconnect 32 and electricalinterconnect 33 and may carry power/signals between power interface 2004and motor/generator system 810 and/or other components in powertransmission system 802. Power interface 2004 may perform the same orsimilar functions as power interface 2002, and may include the same orsimilar components as power interface 2002, including a variablefrequency drive to vary the speed of the motor/generator system 810components, breakers to make or break connections directly to anelectrical gird or other power source or load through interconnect 27,breakers to make or break connections between the variable frequencydrive and the motor/generator system 810 components and/or theelectrical grid, power transformers, and power conditioning equipment.

Working fluid loop 300C may include the same components and subsystems,perform the same or similar functions, and operate substantially thesame or similar to working fluid loop 300. As illustrated, for examplein FIGS. 27, 28, and as describe previously, working fluid loop 300Cincludes a high-pressure high-temperature (HP-HT) fluid path 909, ahigh-pressure medium-temperature (HP-MT) fluid path 910, a low-pressuremedium-temperature (LP-MT) fluid path 912, and a low-pressurelow-temperature (LP-LT) fluid path 911.

In the PHES system 1003, working fluid loop 300C may act as aclosed-cycle fluid path through which the working fluid circulates andin which desired system pressures of the working fluid can bemaintained. The working fluid loop 300C provides an interface for theworking fluid between the SPT system 800 turbomachinery (e.g.,compressor system 830 and turbine system 840 and the heat exchangers inthe main heat exchanger system 300A. In a preferred embodiment, theworking fluid is air. Example embodiments, and portions thereof, ofworking fluid loop 300C, are illustrated in FIGS. 27, 28, 28A, and 28B.

The main heat exchanger system 300A, the HTS system 501, and the CTSsystem 601, may include components, and function, as described withrespect to PHES system 1000 and elsewhere herein.

Components in PHES system 1003 and site integration system 2000,including but not limited to valves, fans, sensors, pumps, heaters, heattraces, breakers, VFDs, working fluid compressors, etc., may each beconnected to a power source and may be independently controllable,either or both proportionally and/or switchably, via one or morecontrollers and/or control systems. Additionally, each such componentmay include, or be communicatively connected via, a signal connectionwith another such component, through, for example, a wired, optical, orwireless connections. For example, a sensor may transmit data regardingtemperature of the working fluid at a location in the working fluidloop; and, a control system may receive that data and responsively senda signal to a valve to close a fluid path. Data transmission andcomponent control via signaling is known in the art and not illustratedherein, except wherein a particular arrangement is new and/orparticularly relevant to the disclosed PHES systems, as with, forexample, FIG. 9.

A. Shared Powertrain System

Unlike PHES system 1000 which includes CPT system 100 as a charge modepowertrain and GPT system 200 as generation mode powertrain, PHES system1003 includes shared powertrain system 800 for both charge mode andgeneration mode operation. Compressor system 830 operates in both chargemode and generation mode, and turbine system 840 operates in both chargemode and generation mode.

In charge mode configuration, SPT system 800 may function as CPT system100 in PHES system 1000, including compressor system 830 functioning ascharge compressor system 130, turbine system 840 functioning as chargeturbine system 140, and power transmission system 802 functioning as thecorresponding motor system 110 and gearbox system 120. In generationmode configuration, SPT system 800 may function as GPT system 200 inPHES system 1000, including compressor system 830 functioning asgeneration compressor system 230, turbine system 830 functioning asgeneration turbine system 240, and power transmission system 802functioning as the corresponding generator system 210 and gearbox system220.

As illustrated in FIGS. 28, 28A, and 28B, working fluid loop 300Cincludes a valve arrangement that allows the working fluid loop 300C toswitch between charge mode operation and generation mode operation.

FIG. 28A illustrates working fluid loop 300C valve states when PHESsystem 1003 is in charge mode (e.g., mode 1002). For charge modeoperation of PHES system 1003, valve 831C1 is open and valve 831G1 isclosed, allowing working fluid to exit the compressor system 830 outletand travel through fluid path 909 to HHX system 500. From HHX system500, working fluid circulates to RHX system 400 and then into fluid path910. Valve 841C1 is open and valve 841G1 is closed, allowing the workingfluid to enter an inlet of turbine system 840. Valve 841C2 is open andvalve 841G2 is closed, allowing working fluid to exit an outlet ofturbine system 840 and travel through fluid path 911 to CHX system 600.From CHX system 600, working fluid bypasses AHX 700 (depending on thestate of valves 323, 324 and/or 325) and circulates through RHX system400 and through fluid path 912. Valve 831C2 is open and valve 831G2 isclosed, allowing working fluid to then enter an inlet of compressorsystem 830, completing the closed loop cycle.

FIG. 28B illustrates working fluid loop 300C valve states when PHESsystem 1003 is in generation mode (e.g., mode 1004). For generation modeoperation of PHES system 1003, valve 831C1 is closed and valve 831G1 isopen, allowing working fluid to exit the compressor system 830 outletand travel through fluid path 910 to RHX system 400. From RHX system400, working fluid circulates through HHX system 500 and then into fluidpath 909. Valve 841C1 is closed and valve 841G1 is open, allowing theworking fluid to enter an inlet of turbine system 840. Valve 841C2 isclosed and valve 841G2 is open, allowing working fluid to exit an outletof turbine system 840 and travel through fluid path 912 to RHX system400. From RHX system 400, working fluid circulates through AHX 700(depending on the state of valves 323, 324 and/or 325), through CHXsystem 600, and through fluid path 911. Valve 831C2 is closed and valve831G2 is open, allowing working fluid to then enter an inlet ofcompressor system 830, completing the closed loop cycle.

ICS 300B may be connected to fluid paths in working fluid loop 300C asillustrated and may function as described elsewhere herein.

Bypass and recirculation loops for SPT system 800, such as the loopscontrolled by valves 119, 132, 222, 229, 401, and 842 may function asdescribed elsewhere herein, for example with respect to PHES system1000.

Sensors 830S, 831S, 840S, 841S, 842S are monitoring and reportingdevices that can provide one or more of pressure, temperature, flowrate, dewpoint, and/or fluid concentration data to one or more controlsystems controlling and/or monitoring conditions of the PHES system1003.

IV. Illustrative PHES System—Reversible Powertrain

FIG. 29 is a top-level schematic diagram of a PHES system 1005 with areversible powertrain, according to an example embodiment, in which PHESsystem and subsystem embodiments herein may be implemented. As atop-level schematic, the example embodiment PHES system 1005 in FIG. 29illustrates major subsystems and select components, but not allcomponents. Additional components are further illustrated with respectto additional figures detailing various subsystems. Additionally oralternatively, in other embodiments, additional components and/orsubsystems may be included, and/or components and/or subsystems may notbe included. FIG. 29 further illustrates select components andsubsystems that work together in the PHES system 1005. FIG. 29schematically shows how the select components and subsystems connect,how they are grouped into major subsystems, and select interconnectsbetween them.

PHES system 1005 utilizes components, fluids, controls, functions,operations, capabilities, systems, subsystems, configurations,arrangements, modes, states, benefits, and advantages described withrespect to PHES system 1000 and 1003, except that PHES system 1005includes a reversible powertrain (“RPT”) system 801 in lieu of the dualpowertrains, CPT system 100 and GPT system 200 or the shared powertrainsystem 800, and a working fluid loop 300D in lieu of working fluid loops300 or 300C.

In FIG. 29, illustrated exemplary components in RPT system 801 includemotor/generator system 810, gearbox system 820, reversible turbomachinesystem 850, and reversible turbomachine system 852. Motor/generatorsystem 810 may include one or more motors, generators, and/ormotor/generators. Gearbox system 820 may include one or more gearboxesconnecting one or more components of the motor/generator system 810 toone or more components of the reversible turbomachine system 850 and/orreversible turbomachine system 852. Reversible turbomachine system 850may include one or more reversible turbomachines. Reversibleturbomachine system 852 may include one or more reversibleturbomachines.

Depending on operational mode, state, and embodiment configuration, RPTsystem 801 may connect to other components and subsystems of PHES system1005 through various interconnects, including electrical interconnect 38and fluid interconnects 34, 34A, 35, 35A, 36, 36A, 37, 37A. Fluidinterconnect pairs 34 and 34A, 35 and 35A, 36 and 36A, 37 and 37A, mayshare common connections between the pairs or may be separate asillustrated. RPT system 801 may include more or fewer interconnects thanshown in FIG. 29. RPT system 801 can accept electrical power in atelectrical interconnect 38 and convert the electrical energy to workingfluid flows through one or more of its fluid interconnects.Additionally, RPT system 801 can output electrical power throughelectrical interconnect 38 as a result of energy generated by RPT system801.

Power/signal path 902 connects electrical interconnect 38 and electricalinterconnect 39 and may carry power/signals between power interface 2006and motor/generator system 810 and/or other components in powertransmission system 802. Power interface 2006 may perform the same orsimilar functions as power interface 2002 and/or 2004, and may includethe same or similar components as power interface 2002 and/or 2004,including a variable frequency drive to vary the speed of themotor/generator system 810 components, breakers to make or breakconnections directly to an electrical gird or other power source or loadthrough interconnect 27, breakers to make or break connections betweenthe variable frequency drive and the motor/generator system 810components and/or the electrical grid, power transformers, and powerconditioning equipment.

Working fluid loop 300D may include the same components and subsystems,perform the same or similar functions, and operate substantially thesame or similar to working fluid loop 300 and/or 300C. As illustrated,for example in FIG. 29, and as describe previously, working fluid loop300D includes a high-pressure high-temperature (HP-HT) fluid path 914, ahigh-pressure medium-temperature (HP-MT) fluid path 915, a low-pressuremedium-temperature (LP-MT) fluid path 917, and a low-pressurelow-temperature (LP-LT) fluid path 916.

In the PHES system 1005, working fluid loop 300D may act as aclosed-cycle fluid path through which the working fluid circulates andin which desired system pressures of the working fluid can bemaintained. The working fluid loop 300D provides an interface for theworking fluid between the RPT system 801 turbomachinery (e.g.,reversible turbomachine system 850 and reversible turbomachine system852 and the heat exchangers in the main heat exchanger system 300A. In apreferred embodiment, the working fluid is air. Example embodiments, andportions thereof, of working fluid loop 300D, are illustrated in FIGS.29, 30, 30A, and 30B.

The main heat exchanger system 300A, the HTS system 501, and the CTSsystem 601, may include components, and function, as described withrespect to PHES systems 1000, 1003 and elsewhere herein.

Components in PHES system 1005 and site integration system 2000,including but not limited to valves, fans, sensors, pumps, heaters, heattraces, breakers, VFDs, working fluid compressors, etc., may each beconnected to a power source and may be independently controllable,either or both proportionally and/or switchably, via one or morecontrollers and/or control systems. Additionally, each such componentmay include, or be communicatively connected via, a signal connectionwith another such component, through, for example, a wired, optical, orwireless connections. For example, a sensor may transmit data regardingtemperature of the working fluid at a location in the working fluidloop; and, a control system may receive that data and responsively senda signal to a valve to close a fluid path. Data transmission andcomponent control via signaling is known in the art and not illustratedherein, except wherein a particular arrangement is new and/orparticularly relevant to the disclosed PHES systems, as with, forexample, FIG. 9.

A. Reversible Powertrain System

Unlike PHES system 1000 which includes CPT system 100 as a charge modepowertrain and GPT system 200 as generation mode powertrain, and PHESsystem 1003 which includes shared powertrain system 800 for both chargemode and generation mode operation with dedicated compressorturbomachinery and dedicated turbine machinery, PHES system 1005includes reversible powertrain system 801 for both charge mode andgeneration mode operation with reversible turbomachines that canalternately act as compressors or turbines depending on the fluid flowdirection, which may depend on the mode and/or state of the PHES system1005.

PHES system 1005 includes reversible powertrain system 801 for bothcharge mode and generation mode operation. Reversible turbomachinesystem 850 includes one or more turbomachines that can operatealternately as a compressor or a turbine and reversible turbomachinesystem 850 operates in both charge mode and generation mode. Reversibleturbomachine system 852 likewise includes one or more turbomachines thatcan operate alternately as a compressor or a turbine and reversibleturbomachine system 852 operates in both charge mode and generationmode.

Depending on the mode, reversible turbomachine system 852 may operate inthe alternate configuration as compared to reversible turbomachinesystem 850. For example, when the PHES system 1005 is in a charge mode,reversible turbomachine system 850 operates as a compressor system andreversible turbomachine system 852 operates as a turbine system. Whenthe PHES system 1005 is in a generation mode, reversible turbomachinesystem 850 operates as a turbine system and reversible turbomachinesystem 852 operates as a compressor system.

In charge mode configuration, RPT system 801 may function as CPT system100 in PHES system 1000, including reversible turbomachine system 850functioning as charge compressor system 130, reversible turbomachinesystem 852 functioning as charge turbine system 140, and powertransmission system 802 functioning as the corresponding motor system110 and gearbox system 120. In generation mode configuration, RPT system801 may function as GPT system 200 in PHES system 1000, includingreversible turbomachine system 852 functioning as generation compressorsystem 230, reversible turbomachine system 850 functioning as generationturbine system 240, and power transmission system 802 functioning as thecorresponding generator system 210 and gearbox system 220.

As illustrated in FIGS. 30, 30A, and 30B, working fluid loop 300Dincludes a valve arrangement that allows for isolation of high-pressurevolume, flow bypass for startup, flow bypass for trip, and otheroperability maneuvers as described elsewhere herein. Unlike PHES system1000 and 1003, this valve arrangement in the working fluid loop 300D isnot needed to switch between charge mode operation and generation modeoperation. Instead, mode switch from charge mode operation to generationmode operation and vice versa is achieved via flow direction reversal,which is done by reversing the rotational direction of RPT system 801.

FIG. 30A illustrates working fluid loop 300D valve states and RPT system801 configuration when PHES system 1005 is in charge mode (e.g., mode1002). For charge mode operation of PHES system 1005, reversibleturbomachine system 850 is operating as a compressor system andreversible turbomachine system 852 is operating as a turbine system.Valve 831 is open, allowing working fluid to exit the reversibleturbomachine system 850 outlet and travel through fluid path 914 to HHXsystem 500. From HHX system 500, working fluid circulates to RHX system400 and then into fluid path 915. Valve 841 is open, allowing theworking fluid to enter an inlet of reversible turbomachine system 852.After expansion in reversible turbomachine system 852, working fluidexits an outlet of reversible turbomachine system 852 and travelsthrough fluid path 916 to CHX system 600. From CHX system 600, workingfluid bypasses AHX 700 (depending on the state of valves 323, 324 and/or325) and circulates through RHX system 400 and through fluid path 917.Working fluid then enters an inlet of reversible turbomachine system850, where it is compressed, completing the closed loop cycle.

FIG. 30B illustrates working fluid loop 300D valve states and RPT system801 configuration when PHES system 1005 is in generation mode (e.g.,mode 1004). For generation mode operation of PHES system 1005,reversible turbomachine system 852 is operating as a compressor systemand reversible turbomachine system 850 is operating as a turbine system.Valve 841 is open, allowing working fluid to exit the reversibleturbomachine system 852 outlet and travel through fluid path 915 to RHXsystem 400. From RHX system 400, working fluid circulates through HHXsystem 500 and then into fluid path 914. Valve 831 is open, allowing theworking fluid to enter an inlet of reversible turbomachine system 852.After expansion in reversible turbomachine system 850, working fluidexits an outlet of reversible turbomachine system 850 and travelsthrough fluid path 917 to RHX system 400. From RHX system 400, workingfluid circulates through AHX 700 (depending on the state of valves 323,324 and/or 325), through CHX system 600, and through fluid path 916.Working fluid then enters an inlet of reversible turbomachine system852, where it is compressed, completing the closed loop cycle.

ICS 300B may be connected to fluid paths in working fluid loop 300D asillustrated and may function as described elsewhere herein.

Bypass and recirculation loops for RPT system 800, such as the loopscontrolled by valves 119, 132, 142, 222, 229, 232, 242, and 401 mayfunction as described elsewhere herein, for example with respect to PHESsystem 1000.

Sensors 850S, 851S, 852S, 853S are monitoring and reporting devices thatcan provide one or more of pressure, temperature, flow rate, dewpoint,and/or fluid concentration data to one or more control systemscontrolling and/or monitoring conditions of the PHES system 1005.

V. Illustrative PHES System—Non-Recuperated

FIGS. 31A and 31B are schematic fluid path diagram of circulatory flowpaths of a non-recuperated main heat exchanger system during charge modeand generation mode, respectively.

The PHES systems (e.g., PHES system 1000, 1003, 1005) disclosed hereinmay be operated without the benefit of a recuperator system (e.g., RHXsystem 400), thus reducing capital costs and flow path complexity andlength. However, removing the recuperator system will generally resultin lower efficiency of the system and/or different temperature profiles(e.g., greater approach temperatures in the remaining heat exchangersystems) across the PHES system.

Main heat exchanger system 300A1 may be substituted for main heatexchanger system 300A in a PHES system, including PHES systems 1000,1003, 1005. Main heat exchanger system 300A1 removes the RHX system frommain heat exchanger system 300A, but is otherwise identical. Theresulting flow paths for charge mode operation and generation modeoperation are shown in FIGS. 31A and 31B, respectively.

VI. Power Transmission Systems

SPT system 800 and RPT system 801 are illustrated in FIGS. 27 and 29 ina particular arrangement for illustrative convenience only, with a powertransmission system 802 and turbomachinery (e.g., 830 and 840, or 850and 852) coaxially in sequence along a common driveshaft. Otherarrangements, including additional components, are possible as well,which may provide advantages compared to the illustrated arrangements ofFIGS. 27 and 29. Each of the power transmission system arrangementsillustrated in FIGS. 32A-32F may be substituted for the arrangements inSPT system 800 and RPT system 801 illustrated in FIGS. 27 and 29. Eachof the power transmission system arrangements illustrated in FIGS.33A-33C may be substituted for the arrangements in SPT system 800illustrated in FIG. 27. For convenience of illustration, each of FIGS.32A-32F and 33A-33C illustrate a single turbomachine of each type (i.e.,830-1, 840-1, 850-1, or 852-1) on a given respective driveshaft;however, multiple additional turbomachines of a given type (i.e., 830-2,840-2, 850-2, or 852-2) may be on a respective driveshaft in alternateembodiments, consistent with the disclosure herein that compressorsystem 830, turbine system 840, reversible turbomachine system 850, andreversible turbomachine system 852 may include one or more turbomachinesof the same type. Multiple turbomachines of a given type on a respectivedriveshaft may be fluidly connected to the working fluid flow in seriesor parallel to, respectively, increase fluid capacity or increasecompression/expansion as in a multi-stage turbomachinery arrangement, orarranged in a combination of series and parallel to accomplish both.

FIG. 32A is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 32A, power transmissionsystem 802 includes a motor/generator 810-1 and a fixed or variablespeed gearbox 820-1 arranged to coaxially drive a common driveshaft 251which turns (or is turned by) the turbomachinery (e.g., compressor 830-1and turbine 840-1, or reversible turbomachine 850-1 and reversibleturbomachine 852-1). The gearbox 820-1 may allow a speed reduction orincrease between the rotating speed of the motor/generator 810-1 and theturbomachinery. Each of the turbomachines, being driven by a commondriveshaft, will rotate at a fixed rate relative to the other. As withCPT system 100 and/or GPT system 200, a turning motor 821-1 and a clutch821-2 may be present in the power transmission system 802, for the samefunctionality and purpose as described with respect to those powertrainsystems 100, 200.

FIG. 32B is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 32B, power transmissionsystem 802 includes a motor/generator 810-1 and a gearbox 820-1 arrangedbetween the turbomachines and driving a common or separate driveshaft(s)251 which turn(s) (or is/are turned by) the turbomachinery (e.g.,compressor 830-1 and turbine 840-1, or reversible turbomachine 850-1 andreversible turbomachine 852-1). The gearbox 820-1 may allow a speedreduction or increase between the rotating speed of the motor/generator810-1 and the turbomachinery. Each of the turbomachines may rotate at afixed rate relative to the other. Gearboxes 820-1A and 820-1B may eachhave one gear ratio used in charge mode and a different gear ratio usedin generation mode. As with CPT system 100 and/or GPT system 200, aturning motor 821-1 and a clutch 821-2 may be present in the powertransmission system 802, for the same functionality and purpose asdescribed with respect to those powertrain systems 100, 200.Beneficially, this arrangement may allow a more compact packaging and/orshorter driveshaft(s) 251, reducing whip in the rotating components(e.g., reducing low-frequency torsional vibration modes). Also, thisarrangement may allow each turbomachine to rotate at different ratesrelative to another, allowing for independent performance optimization.

FIG. 32C is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 32C, power transmissionsystem 802 includes a motor/generator 810-1 and two fixed or variableratio gearboxes 820-1A, 820-1B arranged between the turbomachines anddriving separate driveshafts 251 which turn (or are turned by) theturbomachinery (e.g., compressor 830-1 and turbine 840-1, or reversibleturbomachine 850-1 and reversible turbomachine 852-1). The gearboxes820-1A, 820-1B may each independently provide a speed reduction orincrease between the rotating speed of the motor/generator 810-1 and theturbomachinery connected to the respective driveshaft 251. Gearboxes820-1A may have a different gear ratio than gearbox 820-1B, allowingeach of the turbomachines to rotate at different rates relative to theother. As with CPT system 100 and/or GPT system 200, turning motors821-1 and clutches 821-2 may be present in the power transmission system802, for the same functionality and purpose as described with respect tothose powertrain systems 100, 200. Beneficially, this arrangement allowsvariability in turbomachine speeds relative to each other, whichprovides design flexibility in the turbomachines, the power generationand charge characteristics of the PHES system, and the pressure andtemperature profiles across each of the turbomachines. For example, thearrangement of FIG. 32C allows an independent or unique speed for eachturbomachine based on PHES system operating mode. More specifically, thearrangement of FIG. 32C allows each turbomachine to be operated atdifferent speeds (e.g., minimum two) for common operating modes, e.g.,charge and generation. This enables the same physical turbomachine toperform the same functions but at different power ratings tailored foreach mode. For example, the charge mode operation may run the compressorturbomachine at a higher speed and the turbine turbomachine at a lowerspeed, and similarly, during the generation mode operation, the samecompressor turbomachine may run at a lower speed and the same turbineturbomachine may run at a higher speed. The speed may be optimized toachieve the best performance of each turbomachine by managing (orvarying) either pressure ratio or flow rate for each operating mode andboth pressure ratio and flow rate may be changed to achieve optimumperformance.

FIG. 32D is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 32D, power transmissionsystem 802 includes a motor/generator 810-1 and a fixed or variableratio gearbox 820-1 arranged between the turbomachines and drivingseparate driveshafts 251 which turn (or are turned by) theturbomachinery (e.g., compressor 830-1 and turbine 840-1, or reversibleturbomachine 850-1 and reversible turbomachine 852-1). Motor/generator810 may be a two-speed motor/generator capable of operating, for examplein grid-synchronous mode, with at least two different speed ratesdepending on operating mode (e.g., by changing between two-pole andfour-pole operation). Motor/generator 810-1 may directly drive onedriveshaft 251 and the gearbox 820-1 may drive the other driveshaft 251.The gearbox 820-1 may provide a speed reduction or increase between therotating speed of the motor/generator 810-1 and the turbomachineryconnected to the gearbox-drive driveshaft 251, allowing each of theturbomachines to rotate at different rates relative to the other. In anSPT system 800, the arrangement of FIG. 32C can provide compressor 830-1speed adjustment by the motor/generator 810-1 and turbine speed 840-1adjustment by the gearbox 820-1. In an RPT system 801, the arrangementof FIG. 32C can provide reversible turbomachine 850-1 speed adjustmentby the motor/generator 810-1 and reversible turbomachine 852-1 speedadjustment by the gearbox 820-1. As with CPT system 100 and/or GPTsystem 200, turning motor 821-1 and clutch 821-2 may be present in thepower transmission system 802, for the same functionality and purpose asdescribed with respect to those powertrain systems 100, 200.Beneficially, this arrangement allows variability in turbomachine speedsrelative to each other, which provides design flexibility in theturbomachines, the power generation and charge characteristics of thePHES system, and the pressure and temperature profiles across each ofthe turbomachines. This arrangement provides the same benefits as FIG.32C and simplifies the overall powertrain by eliminating one gearbox,but additionally requires a two-speed motor/generator 810-1.

FIG. 32E is a schematic diagram of a power transmission system,according to an example embodiment. The arrangement of FIG. 32E is avariant of the arrangement in FIG. 32D. In FIG. 32E, power transmissionsystem 802 includes a motor/generator 810-1 and a fixed or variableratio gearbox 820-1 arranged between the turbomachines and drivingseparate driveshafts 251 which turn (or are turned by) theturbomachinery (e.g., compressor 830-1 and turbine 840-1, or reversibleturbomachine 850-1 and reversible turbomachine 852-1). Motor/generator810-1 may be a two speed motor/generator capable of operating, forexample in grid-synchronous mode, with at least two different speedrates depending on operating mode (e.g. by changing between two-pole andfour-pole operation). Motor/generator 810-1 may directly drive onedriveshaft 251 and the gearbox 820-1 may drive the other driveshaft 251.The gearbox 820-1 may provide a speed reduction or increase between therotating speed of the motor/generator 810-1 and the turbomachineryconnected to the gearbox-drive driveshaft 251, allowing each of theturbomachines to rotate at different rates relative to the other. In anSPT system 800, the arrangement of FIG. 32C can provide compressor 830-1speed adjustment by the gearbox 820-1 and turbine speed 840-1 adjustmentby the motor/generator 810-1. In an RPT system 801, the arrangement ofFIG. 32C can provide reversible turbomachine 850-1 speed adjustment bythe gearbox 820-1 and reversible turbomachine 852-1 speed adjustment bythe motor/generator 810-1. As with CPT system 100 and/or GPT system 200,turning motor 821-1 and clutch 821-2 may be present in the powertransmission system 802, for the same functionality and purpose asdescribed with respect to those powertrain systems 100, 200.Beneficially, this arrangement allows variability in turbomachine speedsrelative to each other, which provides design flexibility in theturbomachines, the power generation and charge characteristics of thePHES system, and the pressure and temperature profiles across each ofthe turbomachines. As with FIG. 32D, this arrangement provides the samebenefits as FIG. 32C and simplifies the overall powertrain byeliminating one gearbox, but additionally requires a two-speedmotor/generator 810-1.

FIG. 32F is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 32F, power transmissionsystem 802 includes a motor/generator 810-1 (which may be only a motorin alternate embodiments) and a fixed or variable speed gearbox 820-1Awhich turn (or are turned by) the turbomachinery (e.g., compressor 830-1or reversible turbomachine 850-1) via a driveshaft 251. Powertransmission system 802 further includes a motor/generator 810-2 (whichmay be only a generator in alternate embodiments) and a fixed orvariable speed gearbox 820-1B which turn (or are turned by) theturbomachinery (e.g., turbine 840-1 or reversible turbomachine 852-1)via a separate driveshaft 251. Each of motor/generator 810-1 and 810-2may be a two speed motor/generator capable of operating, for example ingrid-synchronous mode, with at least two different speed rates dependingon operating mode (e.g. by changing between two-pole and four-poleoperation). The gearboxes 820-1A, 820-1B may each independently providea speed reduction or increase between the rotating speed of themotor/generators 810-1, 810-2 and the turbomachinery connected to theirrespective driveshaft 251. Gearboxes 820-1A may have a different gearratio than gearbox 820-1B, allowing each of the turbomachines to rotateat different rates relative to the other. As with CPT system 100 and/orGPT system 200, turning motors 821-1 and clutches 821-2 may be presentin the power transmission system 802, for the same functionality andpurpose as described with respect to those powertrain systems 100, 200.Beneficially, this arrangement allows variability in turbomachine speedsrelative to each other, which provides design flexibility in theturbomachines, the power generation and charge characteristics of thePHES system, and the pressure and temperature profiles across each ofthe turbomachines. Further, this arrangement provides design flexibilityin the motor/generator specifications. This arrangement allows eachturbomachine to operate at an optimum speed either via a variable-speedor two-speed gearbox or via a two-speed motor/generator.

FIGS. 33A-33C each provide arrangements that allow variable speedoperation through the use of controllable clutches. In each of FIGS.33A-33C, the additional motor 811-1 or generator 812-1 can be of smallersize (e.g., smaller power) compared to motor/generator 810-1.

FIG. 33A is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 33A, the arrangementincludes a motor/generator 810-1 and a fixed or variable ratio gearbox820-1 which turn (or are turned by) turbine 840-1 via a driveshaft 251.The arrangement further includes a motor 811-1 and a controllable clutch837, which when the clutch 837 is engaged, turns the compressor 830-1via a separate driveshaft 251. Compressor 830-1 and turbine 840-1 may berotatably connected via a controllable clutch 836. The gearbox 820-1 mayprovide a speed reduction or increase between the rotating speed of themotor/generator 810-1 and the turbine 840-1. The speed of theturbomachines 830-1, 840-1 can be varied with respect to each otherand/or based on the operational mode of the PHES system (e.g., charge orgeneration mode). Rotational speed can be managed via the fixed orvariable ratio gearbox 820-1 and/or motor/generator 810-1, allowing thearrangement to operate with at least three different speeds. Forexample, with clutch 836 engaged and clutch 837 disengaged,motor/generator 810-1 can drive the turbomachines at a first speedthrough the gearbox 820-1. If gearbox 820-1 is a variable speed gearbox,the gearbox 820-1 can be shifted to a different speed, allowing theturbomachines to operate at a second speed. Further, clutch 836 can bedisengaged and clutch 837 engaged, allowing the motor 811-1 to drivecompressor 830-1 at one speed while the turbine 840-1 connected to themotor/generator 810-1 is driven (or drives the motor/generator 810-1) ata different speed. In one example, with the PHES system in charge mode,clutches 836 and 837 are engaged, and compressor 830-1 and turbine 840-1are driven by motor/generator 810-1 at the same speed. In anotherexample, with the PHES system in generation mode, clutch 836 isdisengaged and clutch 837 is engaged, allowing motor 811-1 to drivecompressor 830-1 at one speed. Additionally, gearbox 820-1 is shifted toa higher speed, allowing motor/generator 810-1 to be driven by theturbine 840-1 at a higher speed than the compressor 830-1. As with CPTsystem 100 and/or GPT system 200, turning motor 821-1 and clutch 821-2may be present in the arrangement, for the same functionality andpurpose as described with respect to those powertrain systems 100, 200.Beneficially, this arrangement allows variability in turbomachine speedsrelative to each other and with respect to operating mode, whichprovides design flexibility in the turbomachines, the power generationand charge characteristics of the PHES system, and the pressure andtemperature profiles across each of the turbomachines. Further, thisarrangement provides design flexibility in the motor/generatorspecifications. This arrangement allows each turbomachine to operate atan optimum speed.

FIG. 33B is a schematic diagram of a power transmission system,according to an example embodiment. The arrangement of FIG. 33B is avariant of the arrangement in FIG. 33A. In FIG. 33B, the arrangementincludes a motor/generator 810-1 and a fixed or variable ratio gearbox820-1 which turn compressor 830-1 via a driveshaft 251. The arrangementfurther includes a generator 812-1 and a controllable clutch 838, whichwhen the clutch 838 is engaged, allows the turbine 840-1 to be turnedvia a separate driveshaft 251. Compressor 830-1 and turbine 840-1 may berotatably connected via a controllable clutch 836. The gearbox 820-1 mayprovide a speed reduction or increase between the rotating speed of themotor/generator 810-1 and the compressor 830-1. The speed of theturbomachines 830-1, 840-1 can be varied with respect to each otherand/or based on the operational mode of the PHES system (e.g., charge orgeneration mode). Rotational speed can be managed via the fixed orvariable speed gearbox 820-1 and/or motor/generator 810-1, allowing thearrangement to operate with at least three different speeds. Forexample, with clutch 836 engaged and clutch 838 disengaged,motor/generator 810-1 can drive the turbomachines at a first speedthrough the gearbox 820-1. If gearbox 820-1 is a variable speed gearbox,the gearbox 820-1 can be shifted to a different speed, allowing theturbomachines to operate at a second speed. Further, clutch 836 can bedisengaged and clutch 838 engaged, allowing the generator 812-1 to bedriven by the turbine 840-1 at one speed while the compressor 830-1connected to the motor/generator 810-1 is driven at a different speed.In one example, with the PHES system in charge mode, clutches 836 and838 are engaged, and compressor 830-1 and turbine 840-1 are driven bymotor/generator 810-1 at the same speed. In another example, with thePHES system in generation mode, clutch 836 is disengaged and clutch 838is engaged, allowing generator 812-1 to be driven by turbine 840-1 atone speed. Additionally, gearbox 820-1 is shifted to a lower speed,allowing motor/generator 810-1 to drive the compressor 830-1 at a lowerspeed than the turbine 840-1. As with CPT system 100 and/or GPT system200, turning motor 821-1 and clutch 821-2 may be present in thearrangement, for the same functionality and purpose as described withrespect to those powertrain systems 100, 200. Beneficially, thisarrangement allows variability in turbomachine speeds relative to eachother and with respect to operating mode, which provides designflexibility in the turbomachines, the power generation and chargecharacteristics of the PHES system, and the pressure and temperatureprofiles across each of the turbomachines. Further, this arrangementprovides design flexibility in the motor/generator specifications. Thisarrangement allows each turbomachine to operate at an optimum speed.

FIG. 33C is a schematic diagram of a power transmission system,according to an example embodiment. In FIG. 33C, the arrangementincludes a motor/generator 810-1 connected via a controllable clutch836A to turbine 840-1, which in turn is connected via controllableclutch 838 to generator 812-1. The arrangement further includes themotor/generator 810-1 connected via a controllable clutch 836B tocompressor 830-1, which in turn is connected via controllable clutch 837to motor 811-1. The speed of the turbomachines 830-1, 840-1 can bevaried with respect to each other and/or based on the operational modeof the PHES system (e.g., charge or generation mode). Rotational speedcan be managed via engaging or disengaging the clutches. In one example,compressor 830-1 and turbine 840-1 can be operated at the same speed byengaging clutches 836A, 836B and disengaging clutches 837, 838. Incharge mode, motor/generator 810-1 drives the turbomachinery and, ingeneration mode, motor/generator 810-1 is driven by the turbomachinery.In another example, in charge mode operation, motor/generator 810-1 candrive compressor 830-1 at one speed by having clutch 837 disengaged andclutch 836B engaged. At the same time, generator 812-1 can be driven byturbine 840-1 at a different speed by having clutch 836A disengaged andclutch 838 engaged. In another example, in generation mode operation,motor 811-1 can drive compressor 830-1 at one speed by having clutch 837engaged and clutch 836B disengaged. At the same time, motor/generator810-1 can be driven by turbine 840-1 at a different speed by havingclutch 836A engaged and clutch 838 disengaged.

Beneficially, this arrangement allows variability in turbomachine speedsrelative to each other and with respect to operating mode, whichprovides design flexibility in the turbomachines, the power generationand charge characteristics of the PHES system, and the pressure andtemperature profiles across each of the turbomachines. Further, thisarrangement provides design flexibility in the motor/generatorspecifications. This arrangement allows each turbomachine to operate atan optimum speed. This configuration doesn't require variable-speed ortwo-speed capability from the motor 811-1, generator 812-1, ormotor/generator 810-1. Gearboxes (not shown) may be coupled betweencomponents to provide desired rotational speed, but the gearboxes can befixed speed while still allowing the arrangement to operate at variablespeeds. Compared to other arrangements, this arrangement does requireboth an additional motor and an additional generator.

VII. Modular Turbomachinery Arrangements

As stated previously, SPT system 800 and RPT system 801 are illustratedin FIGS. 27 and 29 in a particular arrangement for illustrativeconvenience only. Other arrangements, including additional components,are possible as well, which may provide advantages compared to theillustrated arrangements of FIGS. 27 and 29. Each of the arrangementsillustrated in FIGS. 34A-34C may be substituted for the SPT system 800arrangement illustrated in FIG. 27, and each of the arrangementsillustrated in FIGS. 35A-35C may be substituted for the RPT system 801arrangement illustrated in FIG. 29. Each of the power transmissionsystem arrangements illustrated in FIGS. 33A-33C may be substituted forthe arrangements in SPT system 800 illustrated in FIG. 27.

The disclosed arrangements in FIGS. 34A-34C and FIGS. 35A-35C utilizesmodular arrangements of turbomachinery for the generation and chargedrivetrains. This is advantageous because PHES system generationpowertrains may benefit from a relatively large turbine system combinedwith a relatively smaller compressor system, and PHES system chargepowertrains may benefit from a relatively large compressor systemcombined with a smaller turbine system. The modular turbomachineryarrangements provided herein address this challenge by combiningmultiple units of, optionally identical, turbomachinery in unequalnumbers depending on the operating mode.

The clutches described with respect to FIGS. 34A-34C and FIGS. 35A-35Care preferably synchro-self-shifting (“SSS”) clutches or other types ofoverrunning clutches, or may alternatively be controllable clutches, ora combination of both types of clutches, or other clutch types as mayprovide benefits to cost, reliability, or operational flexibility.

FIG. 34A is a schematic diagram of modular turbomachinery with sharedpowertrains in a 2×2 configuration, according to an example embodiment.In FIG. 34A, the arrangement includes a first power transmission system802 coupled to a compressor 830-1 and coupled to a turbine 840-1 via aclutch 845. The power transmission system 802 may be, for example, apower transmission system described with respect to FIGS. 32B-32F. Thearrangement further includes a second power transmission system 802coupled to a second compressor 830-2 via a clutch 835 and coupled to asecond turbine 840-2. In an alternative embodiment, second powertransmission system 802 may also be the first power transmission system802 instead of a separate power transmission system 802 as illustrated.Compressor 830-1 is fluidly coupled to interconnects 31 and 28.Compressor 830-2 may be fluidly connected to interconnects 31 and 28,depending on the state of valves 834. With valves 834 closed, compressor830-2 is disconnected from the working fluid loop of the PHES system. Afluid connection is also available to various bypass and recirculationloops described elsewhere herein via interconnects 28A and 31A. Turbine840-2 is fluidly coupled to interconnects 30 and 29. Turbine 840-1 maybe fluidly connected to interconnects 30 and 29, depending on the stateof valves 844. With valves 844 closed, turbine 840-1 is disconnectedfrom the working fluid loop of the PHES system. A fluid connection isalso available to various bypass and recirculation loops describedelsewhere herein via interconnects 29A and 30A.

In generation mode, the arrangement operates with only compressor 830-1and both of the turbines 840-1, 840-2 active. This occurs with clutch835 disengaged and clutch 845 engaged. Turbine 840-1 may be startedeither through control of flow and heat input to the turbine 840-1 orthrough the use of an additional starter motor (e.g. a turning motor821-1, not shown).

In charge mode, the arrangement operates with both compressors 830-1,830-2 and only turbine 840-2 active. This occurs with clutch 835 engagedand clutch 845 disengaged. Compressor 830-2 may be started through theuse of an additional starter motor (e.g. a turning motor 821-1, notshown).

FIG. 35A is a schematic diagram of modular turbomachinery withreversible powertrains in a 2×2 configuration, according to an exampleembodiment. The arrangement of FIG. 35A is a variant of the arrangementin FIG. 34A, but applicable to reversible powertrains. In FIG. 35A, thearrangement includes a first power transmission system 802 coupled to areversible turbomachine 850-1 and coupled to a reversible turbomachine852-1 via a clutch 845. The power transmission system 802 may be, forexample, a power transmission system described with respect to FIGS.32B-32F. The arrangement further includes a second power transmissionsystem 802 coupled to a second reversible turbomachine 850-2 via aclutch 835 and coupled to a second reversible turbomachine 852-1. In analternative embodiment, second power transmission system 802 may also bethe first power transmission system 802 instead of a separate powertransmission system 802 as illustrated. Reversible turbomachine 850-1 isfluidly coupled to interconnects 37 and 34. Reversible turbomachine850-2 may be fluidly connected to interconnects 37 and 34, depending onthe state of valves 834. With valves 834 closed, reversible turbomachine850-2 is disconnected from the working fluid loop of the PHES system. Afluid connection is also available to various bypass and recirculationloops described elsewhere herein via interconnects 28A and 31A.Reversible turbomachine 852-2 is fluidly coupled to interconnects 36 and35. Reversible turbomachine 852-1 may be fluidly connected tointerconnects 36 and 35, depending on the state of valves 844. Withvalves 844 closed, reversible turbomachine 852-1 is disconnected fromthe working fluid loop of the PHES system. A fluid connection is alsoavailable to various bypass and recirculation loops described elsewhereherein via interconnects 35A and 36A.

In generation mode, the arrangement may operates with only reversibleturbomachine 852-1 (acting as a compressor) and both of the reversibleturbomachines 850-1, 850-2 (acting as turbines) active. This occurs withclutch 835 engaged and clutch 845 disengaged. Reversible turbomachine850-1 may be started either through control of flow and heat input tothe reversible turbomachine 850-1 or through the use of an additionalstarter motor (e.g. a turning motor 821-1, not shown).

In charge mode, the arrangement may operate with both reversibleturbomachines 850-1, 850-2 (acting as compressors) and only reversibleturbomachine 852-2 (acting as a turbine) active. This occurs with clutch835 engaged and clutch 845 disengaged. Reversible turbomachine 850-2 maybe started either through control of flow and heat input to thecompressor 830-2 or through the use of an additional starter motor (e.g.a turning motor 821-1, not shown), particularly if an SSS clutch is usedfor clutch 835.

FIG. 34B is a schematic diagram of modular turbomachinery with sharedpowertrains in a 3×2 configuration, according to an example embodiment.In FIG. 34B, the arrangement includes the arrangement of FIG. 34A plusthird power transmission system 802 coupled to a third compressor 830-3.In an alternative embodiment, third power transmission system 802 mayalso be the first power transmission system 802 instead of a separatepower transmission system 802 as illustrated. Compressor 830-1 isfluidly coupled to interconnects 31 and 28.

This 3×2 configuration can be utilized for asymmetric charge/generationapplications where a faster charge profile is desired. In thisconfiguration, as an example, generation mode could operate in a 1×2configuration while charge mode could operate in a 3×1 configuration.

As an example, in generation mode, the arrangement operates with onlycompressor 830-1 and both of the turbines 840-1, 840-2 active. Thisoccurs with clutch 835 disengaged, clutch 845 engaged, and the thirdpower transmission system 802, which is coupled to compressor 830-3, notactively supplying power to compressor 830-3. In an alternativearrangement, an arrangement of valves 834 may be arranged aroundcompressor 830-3, similarly to how they are arranged around compressor830-2, to prevent working fluid flow through compressor 830-3 ingeneration mode.

In charge mode, the arrangement operates with all compressors 830-1,830-2, 830-3 and only turbine 840-2 active. This occurs with clutch 835engaged, clutch 845 disengaged, and the third power transmission system802, which is coupled to compressor 830-3, actively supplying power tocompressor 830-3. In further embodiments, a 4×2 configuration or otherasymmetric configurations can similarly be implemented to enabledifferent asymmetries or increased output.

FIG. 35B is a schematic diagram of modular turbomachinery with areversible powertrain in a 3×2 configuration, according to an exampleembodiment. The arrangement of FIG. 35B is a variant of the arrangementin FIG. 34B, but applicable to reversible powertrains. In FIG. 35B, thearrangement includes the arrangement of FIG. 35A plus third powertransmission system 802 coupled to a third reversible turbomachine850-3. In an alternative embodiment, third power transmission system 802may also be the first power transmission system 802 instead of aseparate power transmission system 802 as illustrated. Third reversibleturbomachine 850-3 is fluidly coupled to interconnects 37 and 34.

This 3×2 configuration can be utilized for asymmetric charge/generationapplications where a faster charge profile is desired. In thisconfiguration, as an example, generation mode could operate in a 1×2configuration while charge mode could operate in a 3×1 configuration.

As an example, in generation mode, the arrangement operates with onlyreversible turbomachine 852-2 (acting as a compressor) and reversibleturbomachines 850-1, 850-2 (acting as turbines) active. This occurs withclutch 835 engaged, clutch 845 disengaged, and the third powertransmission system 802, which is coupled to reversible turbomachine850-3, not actively supplying power to reversible turbomachine 850-3. Inan alternative arrangement, an arrangement of valves 834 may be arrangedaround reversible turbomachine 850-3, similarly to how they are arrangedaround reversible turbomachine 850-3, to prevent working fluid flowthrough reversible turbomachine 850-3 in generation mode.

In charge mode, the arrangement operates with all reversibleturbomachines 850-1, 850-2, 850-3 (acting as compressors) and onlyreversible turbomachine 852-2 (acting as a turbine) active. This occurswith clutch 835 engaged, clutch 845 disengaged, and the third powertransmission system 802, which is coupled to reversible turbomachine850-3, actively supplying power to reversible turbomachine 850-3. In analternative embodiment, reversible turbomachine 852-1 can be removedfrom the arrangement if it is only intended to run in the exemplary 1×2generation configuration and 3×1 charge configuration. However, infurther embodiments, a 3×2 charge configuration could be implemented.

In addition to the embodiments explicitly illustrated in FIGS. 34A, 34B,35A, and 35B, a 4×2 configuration or multiple other asymmetricconfigurations can similarly be implemented by following the embodimentsdescribed herein to enable different asymmetries or increased output.

FIG. 34C is a schematic diagram of modular turbomachinery with a sharedpowertrain in a series configuration, according to an exampleembodiment. In FIG. 34C, the arrangement includes a power transmissionsystem 802 coupled to a compressor 830-1 and coupled to a turbine 840-1.Compressor 830-1 may further be coupled to a second compressor 830-2 viaa clutch 835. Additionally, turbine 840-1 may further be coupled to asecond turbine 840-2 via a clutch 845. The power transmission system 802may be, for example, a power transmission system described with respectto FIGS. 32B-32F. Compressor 830-1 is fluidly coupled to interconnects31 and 28. Compressor 830-2 may be fluidly connected to interconnects 31and 28, depending on the state of valves 834. With valves 834 closed,compressor 830-2 is disconnected from the working fluid loop of the PHESsystem. A fluid connection is also available to various bypass andrecirculation loops described elsewhere herein via interconnects 28A and31A. Turbine 840-1 is fluidly coupled to interconnects 30 and 29.Turbine 840-2 may be fluidly connected to interconnects 30 and 29,depending on the state of valves 844. With valves 844 closed, turbine840-2 is disconnected from the working fluid loop of the PHES system. Afluid connection is also available to various bypass and recirculationloops described elsewhere herein via interconnects 29A and 30A.

In generation mode, the arrangement operates with only compressor 830-1and both of the turbines 840-1, 840-2 active. This occurs with clutch835 disengaged and clutch 845 engaged. Turbine 840-1 may be startedeither through control of flow and heat input to the turbine 840-1 orthrough the use of an additional starter motor (e.g. a turning motor821-1, not shown).

In charge mode, the arrangement operates with both compressors 830-1,830-2 and only turbine 840-1 active. This occurs with clutch 835 engagedand clutch 845 disengaged. Compressor 830-2 may be started through useof an additional starter motor (e.g. a turning motor 821-1, not shown).

In this arrangement, initial spin-up may involve all turbomachinery foreach mode, with all turbomachinery coming to a standstill before modeswitch. Alternatively, initial spin-up could take place with justcompressor 830-1 and turbine 840-1 driven by the power transmissionsystem 802, with compressor 830-2 later engaged via clutch 835 forcharge mode operation or turbine 840-2 later engaged via clutch 845 forgeneration mode operation. For the latter alternative spin up scenario,the clutches ideally are controlled-engagement viscous-style or someother controllable and variable torque clutch that would allow, alongwith controlled opening/closing of the compressor or turbines respectivehigh-pressure-side isolation valve, for a controlled spin-up orspin-down of the engaging/dis-engaging turbomachine.

FIG. 35C is a schematic diagram of modular turbomachinery with areversible powertrain in a series configuration, according to an exampleembodiment. The arrangement of FIG. 35C is a variant of the arrangementin FIG. 34C, but applicable to reversible powertrains. In FIG. 35C, thearrangement includes a power transmission system 802 coupled to areversible turbomachine 850-1 and coupled to a reversible turbomachine852-1. Reversible turbomachine 850-1 may further be coupled to a secondreversible turbomachine 850-2 via a clutch 835. Additionally, reversibleturbomachine 852-1 may further be coupled to a second reversibleturbomachine 852-2 via a clutch 845. The power transmission system 802may be, for example, a power transmission system described with respectto FIGS. 32B-32F. Reversible turbomachine 850-1 is fluidly coupled tointerconnects 37 and 34. Reversible turbomachine 850-2 may be fluidlyconnected to interconnects 37 and 34, depending on the state of valves834. With valves 834 closed, reversible turbomachine 850-2 isdisconnected from the working fluid loop of the PHES system. A fluidconnection is also available to various bypass and recirculation loopsdescribed elsewhere herein via interconnects 37A and 34A. Reversibleturbomachine 852-1 is fluidly coupled to interconnects 36 and 35.Reversible turbomachine 852-2 may be fluidly connected to interconnects36 and 35, depending on the state of valves 844. With valves 844 closed,reversible turbomachine 852-2 is disconnected from the working fluidloop of the PHES system. A fluid connection is also available to variousbypass and recirculation loops described elsewhere herein viainterconnects 36A and 35A.

In generation mode, the arrangement may operates with only reversibleturbomachine 852-1 (acting as a compressor) and both of the reversibleturbomachines 850-1, 850-2 (acting as turbines) active. This occurs withclutch 835 engaged and clutch 845 disengaged. Reversible turbomachine850-2 may be started through the use of an additional starter motor(e.g. a turning motor 821-1, not shown).

In charge mode, the arrangement may operate with both reversibleturbomachine 850-1, 850-2 (acting as compressors) and only reversibleturbomachine 852-1 (acting as a turbine) active. This occurs with clutch835 engaged and clutch 845 disengaged. Reversible turbomachine 850-2 maybe started either through control of flow and heat input to thereversible turbomachine 850-2 or through the use of an additionalstarter motor (e.g. a turning motor 821-1, not shown), particularly ifan SSS clutch is used for clutch 835.

In an alternative embodiment, reversible turbomachine 852-2 can beremoved from the arrangement if it is only intended to run in theexemplary 1×2 generation configuration and 2×1 charge configuration.

In another alternative embodiment, the configuration of FIG. 35C can beused to dramatically and rapidly increase power levels by convertingfrom a single compressor and single turbine flow configuration to a dual(or multiple) compressor and dual (or multiple) turbine flowconfiguration.

VIII. Operating Modes and States in a PHES System

Disclosed herein are various modes of operation and states of a PHESsystem, each of which may be implemented in the exemplary PHES system1000.

A. Primary Modes of Operation

The PHES systems herein, including PHES system 1000, can transitionthrough a number of modes of operation. Each of the primary modes ofoperation can be described with respect to a particular state ofcomponents and subsystems in the PHES system. Additionally, each of theprimary modes of operation has an associated active parasitic load and areadiness time. Example primary modes of operation of the disclosed PHESsystems are shown in FIG. 10.

FIG. 10 illustrates primary modes of operation of a PHES system,including PHES system 1000, according to an example embodiment. Theprimary modes of operation include charge 1002, generation 1004, hotturning 1006, hot standby 1008, cold dry standby 1010, and tripped 1012.FIG. 10 further illustrates the preferred transitions between modes, asindicated by directional arrows between modes. For example, in oneembodiment, a PHES system, such as PHES system 1000, can transition fromcharge 1002 to hot turning 1006 to hot standby 1008 to cold dry standby1010. In another example, a PHES system, such as PHES system 1000, cantransition from charge 1002 to hot turning 1006 to generation 1004.

Cold Dry Standby Mode 1010.

In this primary mode of operation, the thermal storage reservoirs areeffectively offline and the associated thermal storage media are attheir lowest practical thermal energy state for a given embodiment. Inembodiments with liquid thermal storage, the thermal storage media maybe drained to their respective tanks and not circulated through the restof the PHES system. In embodiments with a hot-side liquid thermalstorage media (e.g., molten salt), the hot-side liquid thermal storagemedia may be kept at a minimum temperature to prevent freezing, whichmay include active heating to maintain this minimum practical thermalenergy state. In embodiments with a coolant as a cold-side liquidthermal storage media, the coolant may be kept at or near environmentalambient temperature. In some embodiments, the remainder of the PHESsystem infrastructure may also be kept at or near environmental ambienttemperature. In some embodiments, pressure in the working fluid loop maybe kept at or near ambient environmental pressure or at a minimumworking fluid pressure P_(standby). In one embodiment, P_(standby) is apressure in the working fluid loop (e.g., working fluid loop 300) belowworking pressure (e.g., during charge or generation modes 1002, 1004)but still sufficient to ensure positive pressure with respect to anyopposite side pressure in HTS medium or CTS medium heat exchangersystems (e.g., HHX system 501 or CHX system 601). MaintainingP_(standby) beneficially prevents any HTS medium or CTS medium fromleaking into the working fluid loop (e.g., through cracked heatexchanger cores).

In Cold Dry Standby mode 1010, a PHES system achieves its lowest activeparasitic load. In some embodiments, there is no significant parasiticload. In some embodiments, heating a hot-side liquid thermal storagemedia to prevent freezing is an active parasitic load. In someembodiments, maintaining a working fluid pressure at P_(standby) greaterthan ambient environmental pressure is an active parasitic load.

Within embodiments of the disclosed PHES systems, including PHES system1000, the readiness time to transition between cold dry standby mode1010 and either charge mode 1002 or generation mode 1004 (via hotstandby mode 1008) is a relatively long time compared to other modetransitions to charge mode 1002 or generation mode 1004.

Hot Standby Mode 1008.

In this primary mode of operation, heat exchangers are primed withthermal storage media. In some embodiments, hot-side and/or cold-sideheat exchangers are filled partially or completely with HTS and/or CTSmedia, respectively. In the case of liquid thermal storage media, thethermal storage media may or may not be continuously flowing through theheat exchangers, preferably at a very low flow rate. One or morehot-side heat exchangers (e.g., HHX system 500) are warmed above ambientenvironmental temperature. In some embodiments, heat traces or otherheaters (e.g., heaters 512, 522) are used to heat the HTS medium, whichin turn warms the hot-side heat exchanger(s). The warmed hot-side heatexchangers may be at or near their steady-state temperature for chargeor generation modes, or may be at an intermediate temperature betweentheir steady-state temperature and ambient environmental temperature.CPT system (e.g., CPT system 100) and GPT system (e.g., GPT system 200)are at zero RPM or substantially zero RPM (e.g., no turning, temporarilyspinning down to eventual zero RPM from a prior state, insubstantialturning as a result of convective currents only, and/or no torque inputfrom motors). In some embodiments, minimum pressure in the working fluidloop is kept at P_(standby), though pressure in the working fluid loop(e.g. working fluid loop 300) may be higher initially upon entering hotstandby mode 1008, depending on the prior mode the PHES system istransitioning from.

In hot standby mode, embodiments of the disclosed PHES systems canexperience active parasitic load from heaters working on the thermalstorage media. In some embodiments, heat traces are active to keep thethermal storage media at or near steady-state temperatures. In someembodiments, maintaining a working fluid pressure at P_(standby) is anactive parasitic load.

Within embodiments of the disclosed PHES systems, including PHES system1000, and beneficially, the readiness time to transition between hotstandby mode 1008 and either charge mode 1002 or generation mode 1004 isrelatively short. For example, the readiness time may be less than 10%of the readiness time for transition from cold dry standby mode 1010 toeither charge mode 1002 or generation mode 1004.

Hot Turning Mode 1006.

In this primary mode of operation, either or both the CPT system and/orGPT system is slow rolling (i.e., CPT and/or GPT turbomachinery isspinning at a minimum speed). In a preferred embodiment, theslow-rolling turbomachinery use recirculation and/or bypass fluid loops,such as the examples disclosed herein, to circulate working fluidthrough the slow-rolling turbomachinery.

Within embodiments of the disclosed PHES systems, including PHES system1000, and beneficially, the readiness time to transition between hotturning mode 1006 and either charge mode 1002 or generation mode 1004 isshorter than the readiness time to transition between hot standby mode1008 and either charge mode 1002 or generation mode 1004.

Charge Mode 1002.

In this primary mode of operation, the CPT system turbomachinery isconnected to the electrical grid and preferably operating at grid speed,i.e., the CPT system is operating at an RPM that synchronizes the motorsystem with the operating frequency of the connected electrical grid. Insome embodiments, the GPT system is at zero RPM or substantially zeroRPM (e.g., no turning, temporarily spinning down to eventual zero RPMfrom prior state, insubstantial turning as a result of convectivecurrents only, and/or no torque input from motors). In some embodiments,the GPT system is at turning speed. In charge mode, thermal storagemedia are substantially at steady-state temperatures and one or morecontrol systems control may modulate power consumption of the disclosedPHES systems by, for example, controlling the pressure of the workingfluid. In another embodiment, one or more control systems may controlCTS medium and/or HTS medium flow rates and/or pressures through themain heat exchanger system to modulate power consumption of thedisclosed PHES systems. In another embodiment, one or more controlsystems control both the pressure of the working fluid and/or CTS mediumand/or HTS medium flow rates and/or pressures to modulate powerconsumption of the disclosed PHES systems.

In charge mode, active parasitic loads include support systems for theheat exchanger systems and any associated fluid loops, support systemsfor CPT system, and in some embodiments, support systems for the GPTsystem if the generation powertrain is turning.

Beneficially, embodiments of the disclosed PHES systems can ramp thecharge mode 1002 power consumption very quickly between full power and asignificantly reduced power consumption level (and vice versa).Additionally, within embodiments of the disclosed PHES systems,including PHES system 1000, and beneficially, the readiness time totransition between charge mode 1002 and generation mode 1004 (or viceversa) via hot turning mode 1006 is shorter than the readiness time totransition between hot standby mode 1008 and either charge mode 1002 orgeneration mode 1004.

Generation Mode 1004.

In this primary mode of operation, the GPT system is connected to theelectrical grid and preferably operating at grid speed, i.e., the GPTsystem is operating at an RPM that synchronizes the generator systemwith the operating frequency of the connected electrical grid. In someembodiments, the charge powertrain is at zero RPM or substantially zeroRPM (e.g., no turning, temporarily spinning down to eventual zero RPMfrom prior state, insubstantial turning as a result of convectivecurrents only, and/or no torque input from motors). In some embodiments,the CPT system is at turning speed. In generation mode, thermal storagemedia are substantially at steady-state temperatures. In generationmode, thermal storage media are substantially at steady-statetemperatures and one or more control systems control may modulate powergeneration of the disclosed PHES systems by, for example, controllingthe pressure of the working fluid. In another embodiment, one or morecontrol systems may control CTS medium and/or HTS medium flow ratesand/or pressures through the main heat exchanger system to modulatepower generation of the disclosed PHES systems. In another embodiment,one or more control systems control both the pressure of the workingfluid and/or CTS medium and/or HTS medium flow rates and/or pressures tomodulate power generation of the disclosed PHES systems.

In generation mode, active parasitic loads include support systems forthe heat exchanger systems and any associated fluid loops, supportsystems for GPT system, and in some embodiments, support systems for theCPT system if the charge powertrain is turning.

Beneficially, embodiments of the disclosed PHES systems can ramp thegeneration mode 1004 power generation very quickly between low power andfull power (and vice versa).

Tripped Mode 1012.

This primary mode of operation is a state of recovery from a trip event.This mode may include spin-down of one or more of the powertrains (e.g.CPT system 100, GPT system 200) from its prior controlled (e.g., hotturning and/or steady-state) speed to a slower or substantially zero RPMspeed. In some embodiments, this mode may further include ventingworking fluid to manage working fluid pressures and/or maintain workingfluid pressures within design and/or safe working limits.

In a tripped mode, active parasitic loads will be consistent withwhatever mode preceded the Tripped mode, except where an activeparasitic load also trips to a failsafe condition with a lower (orhigher) load of the active parasitic loads. PHES system readinessexiting from tripped mode 1012 to another mode will vary depending onthe initiating trip event.

B. PHES System Operating States and Transitional States Operating States

FIG. 11 is a state diagram illustrating operating states of a PHESsystem, including PHES system 1000, according to an example embodiment.FIG. 11 mirrors the primary modes of operation shown in FIG. 10,including the preferred transitions between modes, as indicated bydirectional arrows between modes. FIG. 11 further adds additional detailregarding state conditions. Operating states are shown as headings inthe blocks in FIG. 11. Some of these states represent different versionsof three common modes of operation (i.e., hot turning 1006, charge 1002,and generation 1004) and account for alternate configurations in whichthe non-primary powertrain may be operating in (e.g., slow rolling ornot slow rolling). The PHES system operating states illustrated in FIG.11 are “holding states” in which the PHES systems spend significanttime.

CHARGE (GPT BASE) 1014 is a charge mode 1002 operating state where theGPT system (e.g., GPT system 200) is at a base level with low or noactivity. Valves associated with GPT system operation are configured ata base level (e.g., for no rotation of the GPT system). The CPT system(e.g., CPT system 100) is in charge mode with CPT turbomachineryrotating at steady state (i.e., operating) speed. Valves associated withthe CPT system are configured for steady state rotation of CPTturbomachinery, including connection to high-pressure working fluidpaths. The hot-side loop is configured for HTS medium to flow from awarm HTS system (e.g., warm HTS system 591) to a hot HTS system (e.g.,hot HTS system 592) via an HHX system (e.g., HHX system 500). Thecold-side loop is configured for CTS medium to flow from a warm CTSsystem (e.g., warm CTS system 691) to a cold CTS system (e.g., cold CTSsystem 692) via a CHX system (e.g., CHX system 600). Ambient cooling ofworking fluid (e.g. AHX system 700) is bypassed.

GENERATION (CPT BASE) 1016 is a generation mode 1004 operating statewhere the CPT system (e.g., CPT system 100) is at a base level with lowactivity. Valves associated with CPT system operation are configured ata base level (e.g., for no rotation of the CPT system). The GPT system(e.g., GPT system 200) is in generation mode with GPT turbomachineryrotating at steady state (i.e., operating) speed. Valves associated withthe GPT system are configured for steady-state rotation of GPTturbomachinery, including connection to high-pressure working fluidpaths. The hot-side loop is configured for HTS medium to flow from thehot HTS system (e.g., hot HTS system 592) to the warm HTS system (e.g.,warm HTS system 591). The cold-side loop is configured for CTS medium toflow from the cold CTS system (e.g., cold CTS system 692) to the warmCTS system (e.g., warm CTS system 691). Ambient cooling of working fluid(e.g. AHX system 700) is active with working fluid circulating throughthe AHX system 700.

CHARGE (GPT SLOW ROLLING) 1026 is a charge mode 1002 operating statewhere the GPT system (e.g., GPT system 200) is slow rolling (i.e., GPTturbomachinery is spinning at a minimum speed). Valves associated withGPT system operation are configured for recirculation of working fluidthrough the GPT system. The CPT system (e.g., CPT system 100) is incharge mode with CPT turbomachinery rotating at operating speed. Valvesassociated with the CPT system are configured for steady-state rotationof CPT turbomachinery, including connection to high-pressure workingfluid paths. The hot-side loop is configured for HTS medium to flow fromthe warm HTS system (e.g., warm HTS system 591) to the hot HTS system(e.g., hot HTS system 592). The cold-side loop is configured for CTSmedium to flow from the warm CTS system (e.g., warm CTS system 691) tothe cold CTS system (e.g., cold CTS system 692). Ambient cooling ofworking fluid (e.g. AHX system 700) is bypassed.

GENERATION (CPT SLOW ROLLING) 1028 is a generation mode 1004 operatingstate where the CPT system (e.g., CPT system 100) is slow rolling (i.e.,CPT turbomachinery is spinning at a minimum speed). Valves associatedwith CPT system operation are configured for recirculation of workingfluid through the CPT system. The GPT system (e.g., GPT system 200) isin generation mode with GPT turbomachinery rotating at operating speed.Valves associated with the GPT system are configured for steady-staterotation of GPT turbomachinery, including connection to high-pressureworking fluid paths. The hot-side loop is configured for HTS medium toflow from the hot HTS system (e.g., hot HTS system 592) to the warm HTSsystem (e.g., warm HTS system 591). The cold-side loop is configured forCTS medium to flow from the cold CTS system (e.g., cold CTS system 692)to the warm CTS system (e.g., warm CTS system 691). Ambient cooling ofworking fluid (e.g. AHX system 700) is active with working fluidcirculating through the AHX system 700.

HOT TURNING (CPT SLOW ROLLING) 1018 is a hot turning mode 1008 operatingstate where CPT system (e.g., CPT system 100) is slow rolling (i.e., CPTturbomachinery is spinning at a minimum speed). Valves associated withCPT system operation are configured for recirculation of working fluidthrough the CPT system. GPT system (e.g., GPT system 200) is at a baselevel with low activity. Valves associated with GPT system operation areconfigured at a base level (e.g., for no rotation of the GPT system).Hot-side and cold-side loops are in standby, where the HTS and CTS mediaare resident in the associated heat exchangers and thermal media loopfluid paths (e.g., HHX system 500 and CHX system 600, respectively).Heat traces on the hot-side loop are turned on as necessary to keep HTSmedium in liquid phase. The ambient heat exchanger system (e.g. AHXsystem 700) is set to active state. AHX valves are set to allow workingfluid circulation through the AHX system, but no working fluid mayactually be circulating through the AHX system due to recirculationand/or base state of the working fluid at the powertrain. With noworking fluid circulation through the AHX system, AHX system fans areturned off.

HOT TURNING (GPT SLOW ROLLING) 1022 is a hot turning mode 1008 operatingstate where GPT system (e.g., GPT system 200) is slow rolling (i.e., GPTturbomachinery is spinning at a minimum speed). Valves associated withGPT system operation are configured for recirculation of working fluidthrough the GPT system. CPT system (e.g., CPT system 100) is at a baselevel with low activity. Valves associated with CPT system operation areconfigured at a base level (e.g., for no rotation of the CPT system).Hot-side and cold-side loops are in standby, where the HTS and CTS mediaare resident in the associated heat exchangers and thermal media loopfluid paths (e.g., HHX system 500 and CHX system 600, respectively).Heat traces on the hot-side loop are turned on as necessary to keep HTSmedium in liquid phase. The ambient heat exchanger system (e.g. AHXsystem 700) is set to active state. AHX valves are set to allow workingfluid circulation through the AHX system, but no working fluid mayactually be circulating through the AHX system due to recirculationand/or base state of the working fluid at the powertrain. With noworking fluid circulation through the AHX system, AHX system fans areturned off.

HOT TURNING (CPT+GPT SLOW ROLLING) 1020 is a hot turning mode 1008operating state where GPT system (e.g., GPT system 200) is slow rolling(i.e., GPT turbomachinery is spinning at a minimum speed) and CPT system(e.g., CPT system 100) is slow rolling (i.e., CPT turbomachinery isspinning at a minimum speed). Valves associated with GPT systemoperation are configured for recirculation of working fluid through theGPT system. Valves associated with CPT system operation are configuredfor recirculation of working fluid through the CPT system. Hot-side andcold-side loops are in standby, where the HTS and CTS media are residentin the associated heat exchangers and thermal media loop fluid paths(e.g., HHX system 500 and CHX system 600, respectively). Heat traces onthe hot-side loop are turned on as necessary to keep HTS medium inliquid phase. The ambient heat exchanger system (e.g. AHX system 700) isset to active state. AHX valves are set to allow working fluidcirculation through the AHX system, but no working fluid may actually becirculating through the AHX system due to recirculation and/or basestate of the working fluid at the powertrain. With no working fluidcirculation through the AHX system, AHX system fans are turned off.

HOT STANDBY 1024 is a hot standby mode 1008 operating state. GPT system(e.g., GPT system 200) is at a base level with low activity. Valvesassociated with GPT system operation are configured at a base level(e.g., for no rotation of the GPT system). CPT system (e.g., CPT system100) is at a base level with low activity. Valves associated with CPTsystem operation are configured at a base level (e.g., for no rotationof the CPT system). Hot-side and cold-side loops are in standby, wherethe HTS and CTS media are resident in the associated heat exchangers andthermal media loop fluid paths (e.g., HHX system 500 and CHX system 600,respectively). Heat traces on the hot-side loop are turned on asnecessary to keep HTS medium in liquid phase. The ambient heat exchangersystem (e.g. AHX system 700) is set to active state. AHX valves are setto allow working fluid circulation through the AHX system, but noworking fluid may actually be circulating through the AHX system due tobase state of the working fluid at the powertrain. With no working fluidcirculation through the AHX system, AHX system fans are turned off.

COLD DRY STANDBY 1030 is a cold dry standby mode 1010 operating state.GPT system (e.g., GPT system 200) is off with no significant activity.Valves associated with GPT system operation are configured at a baselevel (e.g., for no rotation of the GPT system). CPT system (e.g., CPTsystem 100) is off with no significant activity. Valves associated withCPT system operation are configured at a base level (e.g., for norotation of the CPT system). HTS and CTS media in hot-side and cold-sideloops, respectively, are drained to HTS and CTS tanks, respectively(e.g., tank(s) 510 and/or 520; tank(s) 610 and/or 620). In oneembodiment, HTS medium 590 in HHX 500 and associated fluid paths isdrained to hot HTS tank 520, and HTS medium 590 in warm HTS tank 510remains in warm HTS tank 510. In another embodiment, CTS medium 690 inCHX 600 and associated fluid paths is drained to warm CTS tank 610, andCTS medium 690 in cold CTS tank 620 remains in cold CTS tank 620.Additionally or alternatively, HTS medium 590 and CTS medium 690 may bepumped between their respective tanks in the same manner as a thermalmedia rebalancing operation. Hot-side and cold-side heat exchangers andassociated thermal media loop fluid paths (e.g., HHX system 500 and CHXsystem 600, respectively) are empty of thermal storage media and HTS andCTS media are not actively circulating. One or more HTS system 501heaters (e.g., heaters 512, 522) are active to maintain HTS mediumresident in tanks (e.g., HTS tanks 510, 520) in liquid state.

Transitional States

In addition to the operating states (i.e., long-term holding states)shown in FIG. 11, there are numerous additional transitionary states.These transitionary states would be within the paths shown by the arrowsin FIG. 11. Between operating states, there may be transitional stateswhere one or more subsystems need to switch to their own respectivestates. The subsystems may change their state (e.g., valve actuation,pump speed change) in specific preferred sequences. These transitionsand the intermediary transitionary states that make up the transitionsare described in more detail below.

C. States of Generation Powertrain and Associated Valves

FIG. 12 and FIG. 13 are state diagrams illustrating select operating andtransitional states of a PHES system, including PHES system 1000, eachaccording to an example embodiment. These are example state transitionsand other embodiments are possible as well. FIG. 12 and FIG. 13 are usedprimarily to illustrate generation powertrain state transitions. Otherexamples are provided herein reflecting other state transitions forother subsystems in a PHES system, for example, FIGS. 19, 20, 21, 22,and 23 and their associated descriptions.

FIG. 12 illustrates transition from the HOT STANDBY state 1024 toGENERATION (CPT BASE) state 1016, with intermediate transitional states1034, 1036, 1038. During the transition from the HOT STANDBY state 1024to GENERATION (CPT BASE) state 1016, the generation powertrain movesfrom the base state, at 1024 and 1034, to spin up to variable frequencydrive state, at 1036, to power generation, at 1038 and 1016. The GPTvalve system moves from its base state, at 1024, to bypassed state, at1034 and 1036 and 1038, and then eventually to the connected state, at1016. Beneficially, this overall transition process enables thegeneration powertrain to move through the spin up state with minimalload.

FIG. 13 illustrates transition from the GENERATION (CPT BASE) state 1016to the HOT TURNING (GPT SLOW ROLLING) state 1022, with intermediatetransitional states 1042 and 1044. During the transition from theGENERATION (CPT BASE) state 1016 to the HOT TURNING (GPT SLOW ROLLING)state 1022 (e.g., due to operator initiated shutdown of the generationmode 1004), the generation powertrain moves through the generationstate, at 1016 and 1042, to the base state, at 1044, and then to theturning state, at 1022. The GPT valve systems move from a connectedstate, at 1016, to a bypass state, at 1042 and 1044, beneficially toallow the turbomachinery speed to drop, and eventually to arecirculation state, at 1022, beneficially to allow the rotor to cooldown.

FIG. 14 further describes the generation powertrain (e.g., GPT system200) states (i.e., GPT states) illustrated in FIGS. 12 and 13. FIG. 14is a state diagram illustrating generation powertrain states of a PHESsystem, including PHES system 1000, according to an example embodiment.

The states in FIG. 14 occur sequentially, for the most part, andcorrespond to startup and grid synchronization of the generationpowertrain. The preferred sequential relationship of these states, withexpected allowable transitions, is indicated by directional arrowsbetween states.

At GPT Base state 1048, the generation powertrain is not driven. It istypically not spinning (i.e., at zero RPM), but it may still be spinningas it comes into this state from another state in which it was spinning.Both generation circuit breakers (e.g., 211, 212) are open. Thegeneration powertrain is ready to be spun.

At GPT Spin Up state 1050, the generation powertrain is connected to,and driven by, the VFD, spinning up to rated speed. For gridconnections, once at grid speed, the generator (e.g., generation system230) may not yet be synchronized to the external electrical grid.

GPT Generation state 1052, is a typical operating state for thegeneration mode 1004. At this state, the generation powertrain isspinning at rated speed (i.e., steady state) and the circuit breaker tothe grid is closed. The generation powertrain is connected to the grid.

GPT Slow Roll state 1054, is a typical state for the generationpowertrain when the PHES system is in charge mode 1002, unless the GPTsystem has cooled to the point that it can be in the base state. At thisstate, the generation powertrain is spinning at a low speed (i.e., slowrolling). A generation turning motor (e.g., 221-1) is on to maintain theslow rotational speed of the generation powertrain.

The generation powertrain states illustrated in FIGS. 12, 13, and 14 canbe further described with respect to the electrical status of the powerinterface 2002. Table I lists power interface 2002 component status forGPT states illustrated in FIGS. 12, 13, and 14.

TABLE I Status GPT GPT GPT GPT Base Spin Up Generation Slow Roll 10481050 1052 1054 VFD 214 Off On Off Off VFD-to-GEN Open Closed Open OpenBreaker 211 GEN grid-connect Open Open Closed Open Breaker 212 GENTurning Off Off Off On Motor 221-1

Transitions between generation powertrain states are described in thefollowing paragraphs, with steps recited in preferred sequence.Component references refer to example embodiment GPT system 200, but thesteps may be applied to other configurations to accomplish the samestate transitions.

GPT Base 1048 to GPT Spin Up 1050.

For this state transition, the working fluid loop valving configurationand pressure must be at the right state before this transition can takeplace, as described below with respect to GPTV states. Power is firstapplied to a motor to spin the generation powertrain. In GPT system 200,VFD-to-generator breaker 211 is closed and VFD 214 is turned on,resulting in the generation powertrain spinning. Generator 210-1 isacting as a motor and accepting current from VFD 214. Compressor 230-1and turbine 240-1 are spinning. The motor speed is then increased viaVFD 214, bringing the generation powertrain up to a grid-synchronousspeed.

GPT Spin Up 1050 to GPT Generation 1052.

This transition is a grid-synchronization transition. Motor (e.g.,generator 210-1 acting as a motor) speed is adjusted through currentcontrol (e.g., at VFD 214) to ensure grid-synchronous speed and toprevent speed overshoot. Motor phase is adjusted (e.g., at VFD 214)until the motor phase is grid synchronous. Power supply from grid tomotor is shutoff (e.g., grid-connect breaker 212 is closed), and themotor then acts as a generator to supply power to the grid (e.g.,VFD-to-generator breaker 211 is opened). The VFD will then startpowering down to zero.

GPT Generation 1052 to GPT Base 1048.

This transition can happen, for example, during both normal shutdown ofthe generation powertrain and during a trip event. Power supply fromgrid to motor is opened (e.g., grid-connect breaker 212 is opened). Oncethe generation powertrain has transitioned into GPT Base 1048 (afteropening of the breaker), the generation powertrain will still bespinning, and will start ramping down to zero speed unless thepowertrain is further transitioned to the GPT Slow Rolling 1054 stateprior to spinning down to zero.

GPT Spin Up 1050 to GPT Base 1048.

This transition could happen, for example, due to a trip signal. The VFD(e.g., VFD 214) is turned off and no longer connected to the generator(e.g., VFD-to-generator breaker 211 is opened). Once the generationpowertrain has transitioned into GPT Base 1048 (after opening of thebreaker), the generation powertrain will still be spinning, and willstart ramping down to zero speed unless the generation powertrain isfurther transitioned to the GPT Slow Rolling 1054 state prior tospinning down to zero

GPT Base 1048 to GPT Slow Rolling 1054.

This transition takes place by turning on the turning motor (e.g.,turning motor 221-1), which turns the drive train (e.g., generationturbomachinery 230-1, 240-1) at a very low, “slow rolling speed” (e.g.,0.1% to 1%, 1% to 5%, or 5% to 10% of steady state generation RPM). Innormal operation, as the drive train ramps down in speed, the turningmotor will be turned on during ramp down to ensure the speed of theturbomachinery drivetrain does not slow down below the slow rollingspeed, or if the speed slows below the slow rolling speed, then it isbrought back to the slow rolling speed. This can be accomplished throughan overrunning clutch (e.g., overrunning clutch 221-2) connected betweenthe turning motor and the drivetrain that disengages when the driverside (e.g. drivetrain) of the clutch is operating at speeds higher thanthe slow rolling speed, and engages when the driver side of the clutchis operating at speeds lower than or equal to the slow rolling speed.This results in the turning motor engaging with the turbine when theturbine reaches the speed of the turning motor. The motor will thenmaintain the slow rolling speed.

GPT Slow Rolling 1054 to GPT Base 1048.

The turning motor (e.g., turning motor 221-1) is turned off. Thegeneration powertrain will subsequently coast down to substantially zerorpm.

GPT Slow Rolling 1054 to GPT Spin Up 1050.

To start the generation startup process with the generation powertrainspinning, the powertrain can transition directly from GPT Slow Rolling1054 to GPT Spin Up 1050 by sequentially connecting the VFD to thegenerator (acting as a motor) (e.g., closing VFD-to-generator breaker211) and turning off the turning motor (e.g., turning motor 221-1).

The generation powertrain transitional states illustrated in FIGS. 12and 13 can also be further described with respect to the valve statesassociated with generation powertrain, including, for example, bypassand recirculation loops.

FIG. 16 is a state diagram illustrating generation powertrain (e.g., GPTsystem 200) valve states (i.e., GPTV states), of a PHES system,including PHES system 1000, from a generation powertrain perspective(e.g., GPT system 200 and associated GPT system 200 bypass/recirculationvalves), according to an example embodiment.

The states in FIG. 16 occur sequentially, for the most part. Thepreferred sequential relationship of these states, with expectedallowable transitions, is indicated by directional arrows betweenstates.

At GPTV Base state 1064, the valves are configured to have bothrecirculation valves and the bypass valves open. This is considered afail-safe state.

At GPTV Recirculation state 1070, the generation working fluid valvesare configured such that they can provide working fluid circulation andany desired heat removal for the generation powertrain (e.g., GPT system200) as it spins at a low rate (e.g., slow rolling speed). Thegeneration powertrain is also isolated from the high-pressure side ofthe working fluid loop (e.g., working fluid loop 300).

At GPTV Bypassed state 1066, the bypass valve is open in addition to theisolation (shutoff) valves. This allows working fluid to bypass thegeneration turbine partially, which allows the control of the turbinepower generation prior to reaching full speed and closing the breaker.Beneficially, this allows the use of a uni-directional VFD (e.g., VFD214).

At GPTV HP Connected state 1068, the generation working fluid valves areconfigured such that working fluid can be circulated between thehigh-pressure side and the low-pressure side via the generationpowertrain. All the working fluid bypass loops are closed to preventloss. Valve 229 is closed but may be in a state where it is ready to beopened quickly to help with anti-surge as necessary in case of a tripevent.

Table II lists valve status for state transitions illustrated in FIGS.12 and 13 and GPTV states illustrated in FIG. 16.

TABLE II Status GPTV GPTV GPTV GPTV Base Recirculation Bypassed HPConnected 1064 1070 1066 1068 Compressor Shutoff Closed Closed Open OpenValve 231 (fails closed) Turbine Shutoff Closed Closed Open Open Valve241 (fails closed) Compressor Bypass Open Closed Open Closed Valve 229(fails open) Compressor Recirc Open Open Closed Closed Valve 232 (failsclosed) Turbine Recirc Open Open Closed Closed Valve 242 (fails open)Bypass Path Closed Closed Closed Closed Valve 222 (fails open) BypassPath Closed Closed Closed Closed Valve 401

Further illustrating the GPTV states, FIGS. 3A, 3B, 3C, and 3D eachillustrate a portion of FIG. 3 encompassing GPT system 200 andassociated bypass/recirculation valves, each according to an exampleembodiment. FIG. 3A illustrates GPTV base state 1064. FIG. 3Billustrates GPTV Bypass state 1066. FIG. 3C illustrates GPTVRecirculation state 1070. FIG. 3D illustrates GPTV HP Connected state1068. Valve positions are indicated in FIGS. 3A, 3B, 3C, and 3D with afilled valve icon representing a closed valve and an unfilled valve iconrepresenting an open valve. For example, in FIG. 3A, valve 231 is closedand valve 232 is open.

Transitions between generation powertrain valve (GPTV) states aredescribed in the following paragraphs, with steps recited in preferredsequence. Component references refer to example embodiments GPT system200 and working fluid loop 300, but the steps may be applied to otherconfigurations to accomplish the same GPTV state transitions.

GPTV Base 1064 to GPTV Recirculation 1070.

Turbine bypass fluid path is closed (e.g., valve 229 is closed).

GPTV Base 1064 to GPTV Bypassed 1066.

Compressor recirculation fluid path and turbine recirculation fluid pathare closed (e.g., valve 232 and valve 242 are closed). Turbine bypassfluid path (e.g., valve 229) remains open to allow working fluid to gothrough the bypass loop. Compressor outlet (shutoff) valve 231 isopened. Turbine inlet (shutoff) valve 241 is opened.

GPTV Bypassed 1066 to GPTV HP Connected 1068.

Turbine bypass fluid path is closed (e.g., valve 229 is closed).

GPTV Bypassed 1066 to GPTV Base 1064.

Generation powertrain recirculation fluid paths are opened (e.g.,recirculation valves 232, 242 are opened). Turbine inlet fluid paths areclosed (e.g., valve 241 is closed). Compressor outlet fluid path isclosed (e.g., valve 231 is closed).

GPTV HP Connected 1068 to GPTV Base 1064.

This transition can happen, for example, due to a trip event. Turbineinlet fluid paths are quickly closed (e.g., valve 241 is quicklyclosed). Turbine bypass fluid path is quickly opened (e.g., valve 229 isquickly opened) to help with anti-surge. Compressor outlet fluid path isclosed (e.g., valve 231 is closed). Generation powertrain recirculationfluid paths are opened (e.g., recirculation valves 232, 242 are opened).

GPTV HP Connected 1068 to GPTV Bypassed 1066.

This transition generally happens during normal shut down. Turbinebypass fluid path is opened (e.g., valve 229 is opened) to help withanti-surge.

GPTV Recirculation 1070 to GPTV Base 1064.

Turbine bypass fluid path is opened (e.g., valve 229 is opened).

D. States of Charge Powertrain and Associated Valves

FIG. 15 is a state diagram illustrating charge powertrain (e.g., CPTsystem 100) states (i.e., CPT states) of a PHES system, including PHESsystem 1000, according to an example embodiment.

The states in FIG. 15 occur sequentially, for the most part. Thepreferred sequential relationship of these states, with expectedallowable transitions, is indicated by directional arrows betweenstates.

At CPT Base state 1056, the charge powertrain is not driven. It istypically not spinning (i.e., at zero RPM), but it may still be spinningas it comes into this state from another state in which it was spinning.Both charge circuit breakers (e.g., 111, 112) are open. The chargepowertrain is ready to be spun.

At CPT Spin Up state 1058, the charge powertrain is connected to, anddriven by, the VFD, spinning up to rated speed. For grid connections,once at grid speed, the motor (e.g., charge motor system 110) is not yetsynchronized to the external electrical grid.

CPT Charge state 1060, is a typical operating state for the charge mode1002. At this state, the charge powertrain is spinning at rated speed(i.e., steady state) and the circuit breaker to the grid is closed. Thecharge powertrain is connected to the grid.

CPT Slow Rolling state 1062, is a typical state for the chargepowertrain when the PHES system is in generation mode 1004, unless theCPT system has cooled to the point that it can be in the base state. Atthis state, the charge powertrain is spinning at a very low, “slowrolling speed” (e.g., 0.1% to 1%, 1% to 5%, or 5% to 10% of steady statecharge RPM). A charge turning motor (e.g., 121-1) is on to maintain theslow rolling speed of the charge powertrain.

The charge powertrain states illustrated in FIG. 15 can be furtherdescribed with reference to the electrical status of the power interface2002, illustrated in FIG. 9, which can control electrical power in theCPT system 100. Table III lists power interface 2002 component status,and charge turning motor, for CPT states illustrated in FIG. 15.

TABLE III Status CPT CPT CPT CPT Base Spin Up Charge Slow Roll VFD 214Off On Off Off VFD-to-CHG-Motor Open Closed Open Open Breaker 111 CHGMotor Grid-connect Open Open Closed Open Breaker 112 CHG Turning MotorOff Off Off On 121-1

Transitions between charge powertrain states are described in thefollowing paragraphs, with steps recited in preferred sequence.Component references refer to example embodiment CPT system 100 andpower interface 2002, but the steps may be applied to otherconfigurations to accomplish the same state transitions.

CPT Base 1056 to CPT Spin Up 1058.

For this state transition, the working fluid loop valving configurationand pressure must be at the right state before this transition can takeplace, as described below with respect to CPTV states. Power is firstapplied to a motor (e.g., motor 110-1) to spin the charge powertrain.For CPT system 100, VFD-to-motor breaker 111 is closed and VFD 214 isturned on, resulting in the charge powertrain spinning. Compressorsystem 1301 and turbine system 140 are spinning. The motor speed is thenincreased via VFD 214, bringing the generation powertrain up to agrid-synchronous speed.

CPT Spin Up 1058 to CPT Charge 1060.

This transition is a grid-synchronization transition. Motor (e.g., motor110-1) speed is adjusted through current control (e.g., at VFD 214) toensure grid-synchronous speed and to prevent speed overshoot. Motorphase is adjusted (e.g., at VFD 214) until the motor phase is gridsynchronous. Power supply from grid to motor is activated (e.g.,grid-connect breaker 112 is closed), and VFD power to motor is stopped(e.g., VFD-to-motor breaker 111 is opened). The VFD will then startpowering down to zero.

CPT Charge 1060 to CPT Base 1056.

This transition happens, for example, during both normal shutdown of thecharge powertrain and during a trip event. Power supply from grid tomotor is halted (e.g., grid-connect breaker 112 is opened). Once thecharge powertrain has transitioned into CPT Base 1056 (upon the openingof the breaker), the charge powertrain will still be spinning, and willstart ramping down to zero speed unless the powertrain is furthertransitioned to the CPT Slow Rolling 1062 state prior to spinning downto zero.

CPT Spin Up 1058 to CPT Base 1056.

This transition could happen, for example, due to a trip signal. The VFD(e.g., VFD 214) is turned off and no longer connected to the motor(e.g., VFD-to-motor breaker 111 is opened). Once the charge powertrainhas transitioned into CPT Base 1056 (upon the opening of the breaker),the charge powertrain will still be spinning, and will start rampingdown to zero speed unless the charge powertrain is further transitionedto the CPT Slow Rolling 1062 state prior to spinning down to zero

CPT Base 1056 to CPT Slow Rolling 1062.

This transition takes place by turning on the turning motor (e.g.,turning motor 121-1), which turns the drivetrain (e.g., chargeturbomachinery 130-1, 140-1) at a low speed (e.g., slow rolling speed).In normal operation, as the drivetrain ramps down in speed, the turningmotor will be turned on during ramp down to ensure the speed of thedrivetrain does not slow down below the minimum speed, or if the speedslows below the minimum speed, then it is brought back to the minimumspeed. This can be accomplished through an overrunning clutch (e.g.,overrunning clutch 121-2) connected between the turning motor and thedrivetrain that disengages when the driver side (e.g., drivetrain) ofthe clutch is operating at speeds higher than a minimum speed (e.g.,slow rolling speed), and engages when the driver side of the clutch isoperating at speeds lower than or equal to a minimum speed (e.g., slowrolling speed). This results in the turning motor engaging with theturbine when the turbine reaches the speed of the turning motor. Themotor will then maintain the low (e.g., slow rolling) speed.

CPT Slow Rolling 1062 to CPT Base 1056.

The turning motor (e.g., turning motor 121-1) is turned off. The chargepowertrain will subsequently coast down to zero rpm.

CPT Slow Rolling 1062 to CPT Spin Up 1058.

To start the charge startup process with the charge powertrain spinning,the powertrain can transition directly from CPT Slow Rolling 1062 to CPTSpin Up 1058 by sequentially connecting the VFD to the motor (e.g.,closing VFD-to-motor breaker 111) and turning off the turning motor(e.g., turning motor 121-1).

Charge powertrain transitional states can also be further described withrespect to the valve states associated with charge powertrain bypass andrecirculation loops.

FIG. 17 is a state diagram illustrating charge powertrain (e.g., CPTsystem 100) valve states (i.e., CPTV states), of a PHES system,including PHES system 1000, from a charge powertrain perspective (e.g.,CPT system 100 and associated CPT system 100 bypass/recirculationvalves), according to an example embodiment.

The states in FIG. 17 occur sequentially, for the most part. Thepreferred sequential relationship of these states, with expectedallowable transitions, is indicated by directional arrows betweenstates.

At CPTV Base state 1072, the valves are configured to have bothrecirculation valves and the bypass valves open. This is considered afail-safe state.

At CPTV Recirculation state 1078, the generation working fluid valvesare configured such that they can provide working fluid circulation andany desired heat removal for the charge powertrain (e.g., CPT system100) as it spins at a slow rate (e.g., slow rolling speed). The chargepowertrain is also isolated from the high-pressure side of the workingfluid loop.

At CPTV Bypassed state 1074, the bypass valve is open in addition to theisolation valves. This allows working fluid to circulate via a bypassloop to reduce load on the charge compressor (e.g., compressor system130).

At CPTV HP Connected state 1076, the charge working fluid valves areconfigured such that working fluid can be circulated between thehigh-pressure side and the low-pressure side via the charge powertrain.All the working fluid bypass loops are closed to prevent loss. Valve 119is closed but in a state where it is ready to be opened quickly to helpwith anti-surge as necessary in case of a trip event.

Table IV lists valve status for CPTV states illustrated in FIG. 17.

TABLE IV Status CPTV CPTV CPTV CPTV HP Base Recirculation BypassedConnected Valve 1072 1078 1074 1076 Compressor Shutoff Closed ClosedOpen Open Valve 131 (fails closed) Turbine Shutoff Closed Closed OpenOpen Valve 141 (fails closed) Compressor Bypass Open Closed Open ClosedValve 119 (fails closed) Compressor Recirc Open Open Closed Closed Valve132 (fails closed) Turbine Recirc Open Open Closed Closed Valve 142(fails open)

Further illustrating the CPTV states, FIGS. 3E, 3F, 3G, and 3H eachillustrate a portion of FIG. 3 encompassing CPT system 100 andassociated bypass/recirculation valves, each according to an exampleembodiment. FIG. 3E illustrates CPTV base state 1072. FIG. 3Fillustrates CPTV Bypass state 1074. FIG. 3G illustrates CPTVRecirculation state 1078. FIG. 3H illustrates CPTV HP Connected state1076. Valve positions are indicated in FIGS. 3E, 3F, 3G, and 3H with afilled valve icon representing a closed valve and an unfilled valve iconrepresenting an open valve. For example, in FIG. 3E, valve 131 is closedand valve 132 is open.

Transitions between charge powertrain valve (CPTV) states are describedin the following paragraphs, with steps recited in preferred sequence.Component references refer to example embodiments CPT system 100 andworking fluid loop 300, but the steps may be applied to otherconfigurations to accomplish the same CPTV state transitions.

CPTV Base 1072 to CPTV Recirculation 1078.

Compressor high-flow recirculation fluid path is closed (e.g., valve 119is closed).

CPTV Base 1072 to CPTV Bypassed 1074.

Compressor recirculation fluid path and turbine recirculation fluid pathare closed (e.g., valve 132 and valve 142 are closed). Compressorhigh-flow recirculation fluid path (e.g., valve 119) remains open toallow working fluid to go through the recirculation loop. Compressoroutlet valve 131 is opened. Turbine inlet valve 141 is opened.

CPTV Bypassed 1074 to CPTV HP Connected 1076.

Compressor high-flow recirculation fluid path is closed (e.g., valve 119is closed).

CPTV Bypassed 1074 to CPTV Base 1072.

Charge powertrain recirculation fluid paths are opened (e.g.,recirculation valves 132, 142 are opened). Turbine inlet fluid path isclosed (e.g., valve 141 is closed). Compressor outlet fluid path isclosed (e.g., valve 131 is closed).

CPTV HP Connected 1076 to CPTV Base 1072.

This transition may happen, for example, due to a trip event. Turbineinlet fluid path is quickly closed (e.g., valve 141 is quickly closed).Compressor high-flow recirculation fluid path is quickly opened (e.g.,valve 119 is quickly opened) to help with anti-surge. Compressor outletfluid path is closed (e.g., valve 131 is closed). Charge powertrainrecirculation fluid paths are opened (e.g., recirculation valves 132,142 are opened).

CPTV HP Connected 1076 to CPTV Bypassed 1074.

This transition can happen, for example, during normal shut down orduring a grid trip event. Compressor high-flow recirculation fluid pathis opened (e.g., valve 119 is opened) to help manage the pressure ratioacross the compressor and avoid compressor surge.

CPTV Recirculation 1078 to CPTV Base 1072.

Compressor high-flow recirculation fluid path is opened (e.g., valve 119is opened).

E. States of Ambient Heat Exchanger and Associated Valves

FIG. 18 is a state diagram illustrating ambient cooler (also referred toas ambient heat exchanger) states (e.g., AHX system 700) of a PHESsystem, including PHES system 1000, according to an example embodiment.The two states in FIG. 18 can transition back-and-forth, as indicated bydirectional arrows between the states.

Example ambient cooler states include, Ambient Cooler Bypassed 1080,Ambient Cooler Active 1082, and Ambient Cooler Off 1084. During AmbientCooler Off 1084, working fluid loop valves regulating working fluid flowpaths into or out of the ambient cooler (e.g., AHX system 700) are allclosed, preventing movement of working fluid into or out of the ambientcooler. Ambient cooler fans, if present, are off. During Ambient CoolerBypassed 1080, working fluid loop valves are configured such that theambient cooler is bypassed by working fluid circulating in the workingfluid loop (e.g. working fluid loop 300). Ambient cooler fans, ifpresent, are off. During Ambient Cooler Active 1082, working fluid loopvalves are configured such that working fluid in the working fluid loopcan enter the ambient cooler. If the working fluid is actuallycirculating through the ambient cooler, the ambient cooler removes heatfrom working fluid in the working fluid loop and exhausts it theenvironment; this state may, for example, be used during generation mode1004 and the bypass state 1080 may, for example, be used during chargemode 1002. Ambient cooler fans, if present, may be used to vary the rateof heat extraction from the working fluid. Ambient cooler fans may beturned on, and may have their speed adjusted, when working fluid isactively circulating through the ambient cooler, and the fans may beturned off if the working fluid is not actively circulating through theambient cooler, regardless of valve configuration.

Alternatively, in other embodiments of PHES systems and/or working fluidloop, an ambient cooler (e.g., AHX system 700) can be configured to becontinuously connected to the working fluid loop (i.e., no bypass stateis available). In these alternative embodiments, the fans or otherequipment (e.g., heat sink fluid flow rate) are used to vary the heatremoval capability of the ambient cooler. For example, during generationmode 1004, ambient cooler fans are turned on to actively remove heatfrom the working fluid, and during generation mode 1002, when ambientcooler fans are turned off, the ambient cooler does not passively removea significant amount of heat from the working fluid.

Table V lists cooler and valve status for ambient cooler (e.g., AHXsystem 700) states illustrated in FIG. 18.

TABLE V Status Ambient Cooler Ambient Cooler Ambient Cooler BypassedActive Off 1080 1082 1084 Bypass Open Closed Closed Valve 323 Cold-sideIsolation Closed Open Closed Valve 324 Recuperator-side Closed OpenClosed Isolation Valve 325 AHX Fans Fan Off Fan On Fan Off

Further illustrating ambient cooler states 1080 and 1082, FIGS. 31 and3J each illustrate a portion of FIGS. 3, 28, and 30 encompassing AHXsystem 700 and associated bypass valves, according to an exampleembodiment. FIG. 3I illustrates ambient cooler bypass state 1080. FIG.3J illustrates ambient cooler active state 1082. Valve positions areindicated in FIGS. 31 and 3J with a filled valve icon representing aclosed valve and an unfilled valve icon representing an open valve. Forexample, in FIG. 3I, valve 324 is closed and valve 323 is open.

In an alternative valve arrangement for the ambient cooler states 1080and 1082, FIGS. 3K and 3L each illustrate a portion of FIGS. 3, 28, and30 but with valve 325 removed. FIG. 3K illustrates ambient cooler bypassstate 1080. FIG. 3L illustrates ambient cooler active state 1082. Valvepositions are indicated in FIGS. 3K and 3L with a filled valve iconrepresenting a closed valve and an unfilled valve icon representing anopen valve. For example, in FIG. 3K, valve 324 is closed and valve 323is open. The valve states in Table V are applicable to both FIGS. 31, 3Jand FIGS. 3K, 3L, with the exception that valve 325 states are notapplicable to FIGS. 3K, 3L.

Transitions between ambient cooler states are described in the followingparagraphs, with steps recited in preferred sequence. Componentreferences refer to example embodiments of AHX system 700 and workingfluid loop 300, but the steps may be applied to other configurations toaccomplish the same ambient cooler state transitions.

Ambient Cooler Bypassed 1080 to Ambient Cooler Active 1082.

This transition may occur, for example, for mode switch from charge mode1002 to generation mode 1004 or from start up (e.g., cold dry standbymode 1010) to hot standby 1024. Isolation valves 324 and 325 (ifpresent) are opened. Bypass valve 323 is closed. If working fluid iscirculating through the ambient cooler (e.g. AHX system 700), fans(e.g., fans in AHX system 700) are turned on and fan speed may becontrolled for desired heat removal.

Ambient Cooler Active 1082 to Ambient Cooler Bypassed 1080.

This transition may occur, for example, for mode switch from generationmode 1004 to charge mode 1002. Isolation valves 324 and 325 (if present)are closed. Bypass valve 323 is opened. Fans (e.g., fans in AHX system700) are turned off.

Ambient Cooler Active 1082 to Ambient Cooler Off 1084.

This transition may occur, for example, for mode switch from hot standby1008 and/or 1024 to cold dry standby 1010 and/or 1030. Isolation valves324 and 325 (if present) are closed. Bypass valve 323 is closed. Fans(e.g., fans in AHX system 700) are turned off.

F. States and Control of PHES System and Inventory Control System

FIG. 24 is a simplified block diagram illustrating components of a PHESsystem 1200. The PHES system 1200 may take the form of, or be similar inform, to any PHES system herein, including PHES system 1000, 1003, 1005,3000. The PHES systems disclosed herein (e.g., 1000, 1003, 1005, 3000)may be implemented in and/or include any or all of the componentsillustrated in PHES system 1200, and/or additional components.

The PHES system 1200 may include one or more sensors 1204, powergeneration and power storage components 1206, a communication system1208, a controller system 1216, one or more processors 1210, and a datastorage 1212 on which program instructions 1214 may be stored. Thecomponents may communicate, direct, and/or be directed, over one or morecommunication connections 1202 (e.g., a bus, network, PCB, etc.).

The power generation and/or storage components 1206 may includepowertrains, mechanical and/or electrical power transmission systems,power busses, turbomachinery, motors, generators, motor/generators,working fluid loops, heat exchanger loops, thermal media loops, thermalstorage reservoirs, and electrical systems as described elsewhereherein.

The sensors 1204 may include a range of sensors, including monitoringand reporting devices that can provide operating conditions of the PHESsystem, including one or more of pressure, temperature, flow rate,dewpoint, turbomachinery speed, fan speed, pump speed, valve state, massflow rate, switch state, voltage, amperage, power, frequency, fluidlevel, and/or fluid concentration data, to one or more control systemsand/or controllers controlling and/or monitoring conditions of a PHESsystem

The control system 1216 can function to regulate and/or control theoperation of the PHES system 1200 in accordance with instructions fromanother entity, control system, and/or based on information output fromthe sensors 1204. The control system 1216 may therefore be configured tooperate various valves, switches/breakers, VFDs, pumps, speed controls,and other components of the PHES system 1200 that adjust the operationof the PHES system 1200. The control system 1216 may be implemented bycomponents in whole or in part in the PHES system 1200 and/or byremotely located components in communication with the PHES system 1200,such as components located at stations that communicate via thecommunication system 1208. The control system 1216 may be implemented bymechanical systems and/or with hardware, firmware, and/or software. Asone example, the control system 1216 may take the form of programinstructions 1214 stored on a non-transitory computer readable medium(e.g., the data storage 1212) and a processor (or processors) 1210 thatexecutes the instructions. The control system 1216 may include the PHESSupervisory Controller 1124 and the ICS Controller 1125, as well asother controllers.

The PHES system 1200 may include a communication system 1208. Thecommunications system 1208 may include one or more wireless interfacesand/or one or more wireline interfaces, which allow the PHES system 1200to communicate via one or more networks. Such wireless interfaces mayprovide for communication under one or more wireless communicationprotocols. Such wireline interfaces may include an Ethernet interface, aUniversal Serial Bus (USB) interface, or similar interface tocommunicate via a wire, a twisted pair of wires, a coaxial cable, anoptical link, a fiber-optic link, or other physical connection to awireline network. The PHES system 1200 may communicate within the PHESsystem 1200, with other stations or plants, and/or other entities (e.g.,a command center) via the communication system 1208. The communicationsystem 1208 may allow for both short-range communication and long-rangecommunication. The PHES system 1200 may communicate via thecommunication system 1208 in accordance with various wireless and/orwired communication protocols and/or interfaces.

The PHES system 1200 may include one or more processors 1210, datastorage 1212, and program instructions 1214. The processor(s) 1210 mayinclude general-purpose processors and/or special purpose processors(e.g., digital signal processors, application specific integratedcircuits, etc.). The processor(s) 1210 can be configured to executecomputer-readable program instructions 1214 that are stored in the datastorage 1212. Execution of the program instructions can cause the PHESsystem 1200 to provide at least some of the functions described herein.

As illustrated in FIG. 24A, one or more control systems may be used tocontrol ICS system 390. The working fluid inventory control system (ICS)is part of the working fluid loop subsystem (e.g., working fluid loop300). The inventory control system may include a compressor, a filteringsystem to condition the working fluid, one or more working fluid tanks,fluid paths, and valves to manage the various requirements from thissystem. Example components of an ICS 390 embodiment, as implemented inworking fluid loop 300, are shown in FIG. 3M. FIG. 3M illustrates aportion of FIGS. 3, 28, and 30 encompassing an inventory control system,according to an example embodiment.

A PHES supervisory controller 1124 may determine and/or direct PHESsystem 1000 modes and/or states, which may include ICS system 390 modesand/or states. Alternatively or additionally, an ICS controller 1125 mayreceive directives from PHES supervisory controller 1124, responsivelyenact changes in ICS 390, and report conditions to PHES supervisorycontroller 1124. For example, a power demand signal can be sent fromPHES supervisory controller 1124 to ICS controller 1125. The ICScontroller 1125 may then determine valve sequences and operations based,for example, on current PHES system conditions and the power demandsignal. Alternatively or additionally, PHES supervisory controller 1124may enact changes in ICS 390. For example, PHES supervisory controller1124 may determine a new power demand level in the PHES system 1000 andresponsively direct valve sequences and operations based, for example,on current PHES system conditions and power requirements, to reach thatpower demand level.

During normal operation, in order to increase power in the PHES system1000, a controller (e.g., controller 1125 and/or controller 1124) canincrease the working fluid pressure. To accomplish this, the controllercan cause the following:

-   -   Open valve 312 to throttle working fluid from low-pressure tank        system 310 into the low-pressure side of the working fluid loop        300. This increases the inlet pressure into the CPT system 100        or GPT system 200, which will, in turn, increase the power of        the PHES system 1000.    -   Determine current PHES system 1000 power level and compare to        the power demand level. This step may be repeated until: (i) the        current power level matches the demand level, or (ii) there is        no more driving head (the pressure in low-pressure tank system        310 is only marginally above the working fluid loop 300 low-side        pressure). The latter stop condition can be determined, for        example, by comparing low-pressure tank system 310 pressure and        working fluid loop 300 low-side pressure, or by determining that        current power levels have ceased increasing. If either of these        stop conditions are met, close valve 312.    -   Determine if further power increase is still required (i.e., the        second stop condition above occurred prior to reaching demand        level). If further power increase is required, open valve 322 to        add working fluid from the high-pressure tank system 320 into        the low-pressure side of the working fluid loop 300. This can be        continued until the PHES system 1000 reaches the demand power        level. The ICS tank systems 310, 320 are preferably sized such        that the PHES system 1000 can get to full power in either charge        mode 1002 or generation mode 1004.

To decrease the power in the PHES system 1000, a controller (e.g.,controller 1125 and/or controller 1124) can decrease the working fluidpressure. To accomplish this, the controller can cause the following:

-   -   Open valve 321 to throttle working fluid from the high-pressure        side of the working fluid loop 300 into high-pressure tank        system 320. This decreases the inlet pressure into the CPT        system 100 or GPT system 200, which will, in turn, decrease the        power of the PHES system 1000.    -   Determine current PHES system 1000 power level and compare to        the power demand level. This step may be repeated until: (i) the        current power level matches the demand level, or (ii) there is        no more driving head (high-pressure side of the working fluid        loop 300 is only marginally above the pressure in high-pressure        tank system 320). The latter stop condition can be determined,        for example, by comparing high-pressure tank system 320 pressure        and working fluid loop 300 high-side pressure, or by determining        that current power levels have ceased decreasing. If either of        these stop conditions are met, close valve 321.    -   Determine if further power decrease is still required (i.e., the        second stop condition above occurred prior to reaching demand        level). If further power decrease is required, open valve 311 to        add working fluid from the high-pressure side of the working        fluid loop 300 into the low-pressure tank system 310. This can        be continued until the PHES system 1000 reaches the demand power        level. The ICS tank systems 310, 320 are preferably sized such        that the system can get to minimum power in either charge mode        1002 or generation mode 1004.

Other functions ICS controller 1125 can perform include bringing theworking fluid loop 300 pressures to a desired pressure (e.g., base,ambient, P_(standby), specific pressure range(s) that are below eitheror both the current pressures in the working fluid high-side fluid pathsand low-side fluid paths) following a normal shutdown or a trip event sothat the PHES system can be restarted.

Following a trip event, a controller (e.g., controller 1125 and/orcontroller 1124) can cause the following:

-   -   Open valve 318 to bleed working fluid from high-pressure working        fluid paths into low-pressure tank system 310. By using large        valve 318 (instead of or in addition to valve 311), this can        reduce the pressure in the high-pressure working fluid paths at        a rate fast enough to help maintain a settle-out pressure below        a threshold limit.    -   Close valve 318 once pressure in low-pressure tank system 310 is        substantially equal to that of the high-pressure working fluid        paths.    -   Open valve 305 and then turn on compressor 303 to draw working        fluid from high-pressure working fluid paths into high-pressure        tank system 320 until the high-pressure working fluid paths are        within a desired high-pressure range.    -   Turn off compressor 303 and then close valve 305.    -   Open valve 304 and then turn on compressor 303 to draw working        fluid from low-pressure working fluid paths into the        high-pressure tank system 320 until the low-pressure working        fluid paths are within a desired low-pressure range.

If the PHES system 1000 is shut down normally, large valve 318 may notneed to be opened because the pressure in the high-pressure workingfluid paths has been slowly reduced during the process to substantiallya base level. Accordingly, a controller (e.g., controller 1125 and/orcontroller 1124) can cause the following:

-   -   Open valve 305 and then turn on compressor 303 to draw working        fluid from high-pressure working fluid paths into high-pressure        tank system 320 until the pressure in high-pressure working        fluid paths are at a base pressure.    -   Turn off compressor 303 and then close valve 305.    -   Open valve 304 and then turn on compressor 303 to draw working        fluid from low-pressure working fluid paths into the        high-pressure tank system 320 until the low-pressure working        fluid paths are at a base pressure. This should take only a        short time because the low-pressure working fluid paths should        already be very close to base pressure.

If the working fluid loop 300 leaks working fluid, to controller (e.g.,controller 1125 and/or controller 1124) can cause additional workingfluid to be added to the working fluid loop 300 as follows. Steps aredescribed as if from a state where all referenced valves are initiallyclosed:

-   -   Open valve 302.    -   Turn on compressor 303 to add working fluid from ambient air        when air is the working fluid or from an external working fluid        make-up reservoir (not shown) into high-pressure tank system 320        until high-pressure tank system 320 reaches a desired pressure.    -   Turn off compressor 303.    -   Close valve 302.    -   Open valve 322 to add working fluid from high-pressure tank        system 320 to low-pressure working fluid paths.    -   Close valve 322.    -   Repeat above steps until the working fluid loop pressure is at a        desired level.

G. States of Hot-Side Loop

FIG. 25 is a state diagram illustrating hot-side loop (also referred toas HTS loop) states of a PHES system, including PHES system 1000,according to an example embodiment. The hot-side loop is the flow pathof circulating HTS medium 590, for example, through HTS system 501 inFIG. 4 and, in some states, HHX system 500 in FIGS. 2, 3, 6A, and 6B.

The states in FIG. 25 occur sequentially, for the most part. Thepreferred sequential relationships of these states are indicated bydirectional arrows between states.

At Drained state 1146, HTS medium 590 in fluid paths, including heatexchangers, has been drained or is being drained into the HTS tanks(e.g., 510 and/or 520). Heat trace 560 is off. When coming out ofdrained state 1146, e.g., to standby state 1138, heat trace 560 may beturned on prior to reintroduction of HTS medium 590 into fluid paths.

At Standby state 1138, the hot-side loop is filled or filling with HTSmedium 590 and is ready for HTS medium 590 to flow. If the loop is notalready filled, then a small flow rate would be temporarily establishedin the appropriate direction in order to fill the fluid paths with HTSmedium 590.

At Flow-to-Hot state 1140, the hot-side loop is configured to allow HTSmedium 590 flow from warm HTS system 591 to hot HTS system 592 (e.g.,from warm HTS tank 510 to hot HTS tank 520 in HTS system 501) via thehot-side heat exchanger(s) (e.g., HHX system 500). Warm pump 530 is onto deliver this flow. Heat trace 560 may be turned off because HTSmedium 590 is already hot. Bypass valve 551 is closed so that HTS medium590 flows through HHX system 500.

At Flow-to-Warm state 1142, the hot-side loop is configured to allow HTSmedium 590 flow from hot HTS system 592 to warm HTS system 591 (e.g.,from hot HTS tank 520 to warm HTS tank 510 in HTS system 501) via thehot-side heat exchanger(s) (e.g., HHX system 500). Hot pump 540 is on todeliver this flow. Heat trace 560 may be turned off because HTS medium590 is already hot. Bypass valve 551 is closed so that HTS medium 590flows through HHX system 500.

At Bypassed state 1144, HTS medium 590 is flowing in the hot-side looppreferably from hot HTS system 592 to warm HTS system 591 (e.g., fromhot HTS tank 520 to warm HTS tank 510 in HTS system 501), but notthrough the hot-side heat exchanger(s) (e.g., HHX system 500). Hot-sideheat exchanger(s) are bypassed by opening bypass valve 551 and closingisolation valves 555, 556. Alternatively, in another embodiment, HTSmedium 590 could flow in the hot-side loop from warm HTS system 591 tohot HTS system 592 (e.g., from warm HTS tank 510 to hot HTS tank 520 inHTS system 501), but not through the hot-side heat exchanger(s) (e.g.,HHX system 500).

Table VI lists equipment status for hot-side loop states illustrated inFIG. 25. Component references refer to example embodiments illustratedin, for example, FIGS. 2, 3, 4, 6A, and 6B, and including HTS system 501and HHX system 500, but the status may be applied to otherconfigurations to accomplish the same hot-side loop state states.

TABLE VI Status Drained Standby Flow-to-Hot Flow-to-Warm Bypassed 11461138 1140 1142 1144 HX Bypass Closed Closed Closed Closed Open Valve 551Heat Trace Off On Off Off Off 560 Warm Pump Off Off On Off *2 530 WarmHeater *1 On On On On 512 Warm Inflow Closed Closed Closed Open *3 Valve511 Warm Pump Closed Open Open Closed *2 Outlet Valve 557 HX Warm ClosedOpen Open Open Closed Isolation Valve 555 Warm Drain Open Closed ClosedClosed Closed Valve 552 Hot Pump Off Off Off On *3 540 Hot Heater *1 OnOn On On 522 Hot Inflow Closed Open Open Closed *2 Valve 521 Hot PumpClosed Closed Closed Open *3 Outlet Valve 558 HX Hot Closed Open OpenOpen Closed Isolation Valve 556 Hot Drain Open Closed Closed ClosedClosed Valve 553 *1 ON if HTS medium present; OFF if HTS medium notpresent *2 ON or OPEN if bypass flow to hot; OFF or CLOSED if bypassflow to warm *3 ON or OPEN if bypass flow to warm; OFF or CLOSED ifbypass flow to hot

H. States of Cold-Side Loop

FIG. 26 is a state diagram illustrating cold-side loop (also referred toas CTS loop) states of a PHES system, including PHES system 1000,according to an example embodiment. The cold-side loop is the flow pathof circulating CTS medium 690, for example, through CTS system 601 inFIG. 5 and, in some states, CHX system 600 in FIGS. 2, 3, 6A, and 6B.

The states in FIG. 26 occur sequentially, for the most part. Thepreferred sequential relationship of these states are indicated bydirectional arrows between states.

At Drained state 1156, CTS medium 690 in fluid paths, including heatexchangers, has been drained or is being drained into the CTS tanks(e.g., 610 and/or 620), preferably into a warm CTS tank (e.g., warm CTStank 610). Preferably, no CTS pump is running once all CTS medium 690has been drained.

At Standby state 1148, the cold-side loop is filled or filling with CTSmedium 690 and is ready for CTS medium 690 to flow. Preferably, no CTSpump is running once the cold-side loop has been filled. If the loop isnot already filled, then a flow rate from pumps 630 and/or 640 would beestablished in the appropriate direction in order to fill the fluidpaths with CTS medium 690.

At Flow-to-Cold state 1150, the cold-side loop is configured to allowCTS medium 690 flow from warm CTS system 691 to cold CTS system 692(e.g., from warm CTS tank 610 to cold CTS tank 620 in CTS system 601)via the cold-side heat exchanger(s) (e.g., CHX system 600). Warm pump630 is on to deliver this flow. Cold pump 640, if bi-directional, canalso be on to assist with pressure control. Bypass valve 605 is closedso that CTS medium 690 flows through CHX system 600.

At Flow-to-Warm state 1152, the cold-side loop is configured to allowCTS medium 690 flow from cold CTS system 692 to warm CTS system 691(e.g., from cold CTS tank 620 to warm CTS tank 610 in CTS system 601)via the cold-side heat exchanger(s) (e.g., CHX system 600). Cold pump640 is on to deliver this flow. Warm pump 630, if bi-directional, canalso be on to assist with pressure control. Bypass valve 605 is closedso that CTS medium 690 flows through CHX system 600.

At Bypassed state 1154, CTS medium 590 is preferably flowing in thecold-side loop from cold CTS system 692 to warm CTS system (e.g., fromcold CTS tank 620 to warm CTS tank 610 in CTS system 601), but notthrough the cold-side heat exchanger(s) (e.g., CHX system 600).Cold-side heat exchanger(s) are bypassed by opening bypass valve 605 andclosing isolation valves 602, 603. Alternatively, in another embodiment,CTS medium 590 could flowing in the cold-side loop from warm CTS systemto cold CTS system 692 (e.g., from warm CTS tank 610 to cold CTS tank620 in CTS system 601), but not through the cold-side heat exchanger(s)(e.g., CHX system 600).

Table VII lists equipment status for cold-side loop states illustratedin FIG. 26, in an embodiment of CTS system 601 where pumps 630, 640 areused for bi-directional pumping. Component references refer to exampleembodiments illustrated in, for example, FIGS. 2, 3, 5, 6A, and 6B andincluding CTS system 601 and CHX system 600, but the status may beapplied to other configurations to accomplish the same hot-side loopstates.

TABLE VII Status Drained Standby Flow-to-Cold Flow-to-Warm BypassedEquipment 1156 1148 1150 1152 1154 Bypass Valve Closed Closed ClosedClosed Open Valve 605 Inert Gas *1 Closed Closed Closed Closed PurgeValve 624 Cold Pump Off Off On to Cold On to Warm *2 640 Cold ClosedOpen Open Open Closed Isolation Valve 602 Cold Tank Closed Open OpenOpen Open Valve 621 Cold Pump Closed Open Open Open Open Isolation Valve641 Cold Pump Closed Closed Closed Closed Closed Bypass Valve 642 ColdPump Closed Open Open Open Open Isolation Valve 643 Warm Pump Off Off Onto Cold On to Warm *2 630 Warm Closed Open Open Open Closed IsolationValve 603 Warm Tank Closed Open Open Open Open Valve 611 Warm PumpClosed Open Open Open Open Isolation Valve 631 Warm Pump Closed ClosedClosed Closed Closed Bypass Valve 632 Warm Pump Closed Open Open OpenOpen Isolation Valve 633 *1 OPEN until purge complete *2 ON-to-Warm ifbypass flow to warm; ON-to-Cold if bypass flow to cold

Table VIII lists equipment status for cold-side loop states illustratedin FIG. 26, in an embodiment of CTS system 601 where pumps 630, 640 arenot used for bi-directional pumping. Component references refer toexample embodiments illustrated in, for example, FIGS. 2, 3, 5, 6A, and6B and including CTS system 601 and CHX system 600, but the status maybe applied to other configurations to accomplish the same hot-side loopstates.

TABLE VIII Status Drained Standby Flow-to-Cold Flow-to-Warm Bypassed1156 1148 1150 1152 1154 Bypass Valve Closed Closed Closed Closed OpenValve 605 Inert Gas *1 Closed Closed Closed Closed Purge Valve 624 ColdPump Off Off Off On to Warm *2 640 Cold Closed Open Open Open ClosedIsolation Valve 602 Cold Tank Closed Open Open Open Open Valve 621 ColdPump Closed Open Closed Open *5 Isolation Valve 641 Cold Pump ClosedClosed Open Closed *4 Bypass Valve 642 Cold Pump Closed Open Closed Open*5 Isolation Valve 643 Warm Pump Off Off On to Cold On to Warm *3 630Warm Closed Open Open Open Closed Isolation Valve 603 Warm Tank ClosedOpen Open Open Open Valve 611 Warm Pump Closed Open Open Closed *4Isolation Valve 631 Warm Pump Closed Closed Closed Open *5 Bypass Valve632 Warm Pump Closed Open Open Closed *4 Isolation Valve 633 *1 OPENuntil purge complete *2 On-to-Warm if bypass flow to warm; OFF if bypassflow to cold *3 On-to-Cold if bypass flow to cold; OFF if bypass flow towarm *4 OPEN if bypass flow to cold; CLOSED if bypass flow to warm *5CLOSED if bypass flow to cold; OPEN if bypass flow to warm

IX. Use Cases

This section describes transient “use cases” that can be implemented ina PHES system, including PHES system 1000 and the subsystems describedherein. Each transient use case is a process or a transitionary sequencethat the PHES system undergoes, and can be described by mode and/orstate changes.

A. Cold Dry Standby to Hot Standby (PHES System Startup)

This use case is illustrated in FIG. 10 as the transition from Cold DryStandby mode 1010 to Hot Standby mode 1008, and in FIG. 11 as thetransition from operating state 1030 to operating state 1024.

B. Hot Standby to Charge (PHES System Startup)

This use case is illustrated in FIG. 10 as the transition from HotStandby mode 1008 to Charge mode 1002, and in FIG. 11 as the transitionfrom operating state 1024 to operating state 1014.

FIG. 19 further illustrates this use case. FIG. 19 is a state diagramillustrating operating and transitional states in a PHES system,including PHES system 1000, according to an example embodiment. Theseare example state transitions and other embodiments are possible aswell. FIG. 19 illustrates transition from the HOT STANDBY state 1024 toCHARGE (GPT BASE) state 1014, with intermediate transitional states1086, 1088, 1090 occurring sequentially in between. Each of thesubsystem states is described elsewhere herein.

C. Hot Standby to Generation (PHES System Startup)

This use case is illustrated in FIG. 10 as the transition from HotStandby mode 1008 to Generation mode 1004, and in FIG. 11 as thetransition from operating state 1024 to operating state 1016.

FIG. 20 further illustrates this use case. FIG. 20 is a state diagramillustrating operating and transitional states in a PHES system,including PHES system 1000, according to an example embodiment. Theseare example state transitions and other embodiments are possible aswell. FIG. 20 illustrates transition from the HOT STANDBY state 1024 toGENERATION (CPT BASE) state 1016, with intermediate transitional states1094, 1096, 1098 occurring sequentially in between. Each of thesubsystem states is described elsewhere herein.

D. Charge to Hot Turning (PHES System Shutdown)

This use case is illustrated in FIG. 10 as the transition from Chargemode 1002 to Hot Turning mode 1006, and in FIG. 11 as the transitionfrom operating state 1014 to operating state 1018.

FIG. 21 further illustrates this use case. FIG. 21 is a state diagramillustrating operating and transitional states in a PHES system,including PHES system 1000, according to an example embodiment. Theseare example state transitions and other embodiments are possible aswell. FIG. 21 illustrates transition from the CHARGE (GPT BASE) state1014 to HOT TURNING (CPT SLOW ROLLING) state 1018, with intermediatetransitional states 1102, 1104 occurring sequentially in between. Eachof the subsystem states is described elsewhere herein.

E. Generation to Hot Turning (PHES System Shutdown)

This use case is illustrated in FIG. 10 as the transition fromGeneration mode 1004 to Hot Turning mode 1006, and in FIG. 11 as thetransition from operating state 1016 to operating state 1022.

FIG. 22 further illustrates this use case. FIG. 22 is a state diagramillustrating operating and transitional states in a PHES system,including PHES system 1000, according to an example embodiment. Theseare example state transitions and other embodiments are possible aswell. FIG. 22 illustrates transition from the GENERATION (CPT BASE)state 1016 to HOT TURNING (GPT SLOW ROLLING) state 1022, withintermediate transitional states 1108, 1110 occurring sequentially inbetween. Each of the subsystem states is described elsewhere herein.

F. Hot Standby to Cold Dry Standby (PHES System Shutdown)

This use case is illustrated in FIG. 10 as the transition from HotStandby mode 1008 to Cold Dry Standby mode 1010 to, and in FIG. 11 asthe transition from operating state 1024 to operating state 1030.

G. Charge to Generation (PHES System Mode Switch)

This use case is illustrated in FIG. 10 as the transition from Chargemode 1002 to Hot Turning mode 1006 to Generation mode 1004, and in FIG.11 as the transition from operating state 1014 to operating state 1018to operating state 1028.

FIG. 23 further illustrates this use case. FIG. 23 is a state diagramillustrating operating and transitional states in a PHES system,including PHES system 1000, according to an example embodiment. Theseare example state transitions and other embodiments are possible aswell.

FIG. 23 illustrates transition from the CHARGE (GPT BASE) state 1014 toHOT TURNING (CPT SLOW ROLLING) state 1018, with intermediatetransitional states 1102, 1104 occurring sequentially in between. FIG.23 further continues with illustration of the continuing transition fromHOT TURNING (CPT SLOW ROLLING) state 1018 to GENERATION (CPT SLOW ROLL)state 1028, with intermediate transitional states 1116, 1118 occurringsequentially in between. Each of the subsystem states is describedelsewhere herein.

X. PHES System Power Plant Integration

Power plants are usually most efficient at their rated power. If a powerplant operates at partial power (due to low demand), the efficiency goesdown. Additionally, thermal power plants, can exhibit relatively longstartup and shutdown times, making it difficult to respond to griddemands. Furthermore, in coal plants, the scrubbing system, which helpsto clean the flue gas, also loses its efficiency at partial power,causing environmentally undesirable emissions. Therefore, there aremultiple benefits to running power plants, and particularly thermalpower plants, at their rated power.

FIGS. 36 and 38 are top-level schematic diagram of a PHES system incharge mode and generation mode, respectively, integrated with a powergeneration plant, according to an example embodiment.

FIGS. 36 and 38 includes a PHES system 3000, which may be any PHESembodiment described herein, including PHES systems 1000, 1003, 1005,1200. The PHES system 3000 is integrated with a power plant 3100 thatgenerates power, preferably for distribution to a power grid. Powerplant can send electrical power to, and/or receive electrical powerfrom, the PHES system 3000 via power/signal paths 3003 and 3004.Power/signal paths 3003 and 3004 may include a station 3007 that cancontrol and/or act on power transmission along the power/signal paths.As non-limiting examples, station 3007 may act as one or more of a powersubstation, a switching station, a distribution substation, and/or acollector substation. Power plant 3100 and the PHES system 3000 arepreferably connected to an electrical grid, which can occur at station3007 or elsewhere, such as through power plant 3100.

In one embodiment, the PHES system 3000 can receive electrical powerfrom the power plant 3100 for driving the powertrains (e.g., 100, 200,800, 801). In another embodiment, the PHES system 3000 can receiveelectrical power from the electrical grid for driving the powertrains(e.g., 100, 200, 800, 801). In another embodiment, the PHES system 3000can switchably receive electrical power from one or both of the powerplant 3100 and/or the electrical grid for driving the powertrains (e.g.,100, 200, 800, 801).

In an embodiment, the PHES system 3000 can receive electrical power fromthe power plant 3100 via power path 3006 for resistive heating of HTSmedium 590. In another embodiment, the PHES system 3000 can receiveelectrical power from the electrical grid via power path 3006 forresistive heating of HTS medium 590. In another embodiment, the PHESsystem 3000 can switchably receive electrical power from one or both ofthe power plant 3100 and the electrical grid via power path 3006 forresistive heating of HTS medium 590.

A. Resistive Heating

FIG. 37A is a schematic diagram of the hot-side thermal storage system501 illustrated in FIGS. 4, 36, 38 integrated with a power generationplant 3100 according to an example embodiment. Power path 3006 suppliesswitchable power to one or more of electric resistive heaters 3016and/or 3017. The resistive heaters 3016, 3017 can accept electricalpower and convert it to thermal energy for heating the hot HTS medium590. Resistive heater 3016 is located in one or more of hot HTS tank520. Resistive heater 3017 is inline to the fluid path controlled byvalve 521 and can accept electrical power and convert it to thermalenergy for heating the hot HTS medium 590 entering one or more of hotHTS tank 520.

The resistive heaters 3016 and/or 3017 can be used to increase the HTSmedium 590 temperature in tank 520. With resistive heaters 3016 and/or3017, the HTS medium 590 temperature can preferably be much hotter(e.g., 800° C.) than the PHES system 3000 can deliver using thethermodynamic charge cycle alone (e.g., 550C to 600C). In one example,the resistive heaters 3016 and/or 3017 can be turned on while the PHESsystem 3000 is in charge mode (e.g., as illustrated in FIG. 36),increasing the hot HTS medium 590 temperature (e.g., from 550° C. to800° C.). In this application, a high-temperature thermal or solar saltmay be used as the HTS medium 590 in order to permit the highertemperatures. This allows the PHES system 3000 to advantageously operatewith a high coefficient of performance from, for example, 250° C. to550° C., while additionally storing more thermal energy in the PHESsystem 3000 due to the resistive heating. Depending on HTS medium 590flow, and the which resistive heater 3016 and/or 3017 is used, resistiveheating can occur with the power plant 3100 in a generation mode andPHES system 3000 in a charge, idle, or generation mode. Advantageously,with the resistive heating, the PHES system 3000 can take additionalload from the power plant (or grid), which allows the PHES system 3000to stay at a desired load even if the PHES system 3000 thermodynamiccycle through the turbomachinery must be turned down partially or fully.As another advantage, a higher hot HTS medium 590 temperature allows thegeneration cycle to exhibit higher efficiency. As another advantage ofthe resistive heating integration, the PHES system 3000 can be charged,even if the charge mode is down for maintenance or it is otherwiseundesirable to run the charge mode at a particular time.

B. PHES System Power Plant Thermal Integration—Charge Mode & Idle Mode

Returning to FIG. 36, additional embodiments are illustrated that caneach be separated from, or combined with, the resistive heatingembodiment. As further illustrated in FIG. 36, the PHES system 3000 canbe thermally integrated with the power plant 3100 during a charge modeor, in some embodiments, in and idle mode. If power plant 3100 is athermal power station, where heat energy is converted to electricalpower, heat energy from the power plant 3100, for example when it is ina generation mode, can be routed into the PHES system 3000.Additionally, heat can be routed out of the PHES system 3000 and intothe power plant 3100, which may occur, for example, when the PHES systemis in a charge mode or an idle mode, and the power plant 3100 is in ageneration mode.

In one embodiment, with the PHES system 3000 in a charge mode and powerplant 3100 in a generation mode, exhaust heat flowing in fluid path 3012from power plant 3100 to charge powertrain system 3001 can be used toreheat working fluid in the charge cycle after a first turbine stage.This embodiment is further illustrated in FIG. 36A.

FIG. 36A is a schematic diagram of a portion of powertrain system 3001thermally integrated with power plant 3100 via fluid path 3012,according to an example embodiment. Powertrain 3001 can be any PHESsystem powertrain disclosed herein for charge mode operation, includingCPT system 100, SPT system 800 in a charge mode configuration, and RPTsystem 801 in a charge mode configuration. For illustrative clarity,only select portions of the powertrain system 3001 are illustrated.Illustrated are compressor inlet interconnects 20,31,37 and compressoroutlet interconnects 17,28,34 for the respective compressor systems 130,830, or 850 (acting as a compressor), and turbine inlet interconnects18,29,35 and turbine outlet interconnects 19,30,36 for the respectiveturbine systems 140, 840, or 852 (acting as a turbine). The turbinesystem (e.g., 140, 840, 852) may include at least two stages,illustrated as turbine pairs 140-1,140-2, or 840-1,840-2, or852-1,852-2. Between the two stages, the working fluid path may passthrough a valve system 3020 which can direct the inter-stage workingfluid to a reheater 3018 or the valve system 3020 can bypass thereheater 3018. Working fluid in the PHES system 3000 expands through thefirst turbine stage (e.g., 140-1) and then enters reheater 3018.Reheater 3018 acts as a heat exchanger, transferring heat to the workingfluid from exhaust heat flowing into reheater 3018 from fluid path 3012,which is connected to the power plant 3100. The exhaust may be dumped toambient or sent elsewhere after passing through the reheater 3018. Theworking fluid, after passing through the reheater 3018, expands throughthe second turbine stage (e.g., 140-2) before exiting the turbine system(e.g., 140).

Additional embodiments of the thermal integration with reheater caninclude multiple reheaters and multiple turbine stages. The number ofturbine stages depends on the exhaust temperature from the power plant3100 as well as a balance between cost and improvements in thecoefficient of performance of the PHES system 3000 charge cycle.

Advantageously, the thermal integration with reheater embodiments canprovide a higher coefficient of performance in the PHES system 3000charge cycle because the turbine system can generate more power.Additionally, using exhaust heat from the power plant 3100 provides alower exhaust temperature if the exhaust is eventually dumped to theambient environment, thus providing less environmental impact.

Returning again to FIG. 36, additional embodiments are illustrated thatcan each be separated from, or combined with, resistive heatingembodiments and/or reheater embodiments. If power plant 3100 is athermal power station, where heat energy is converted to electricalpower, heat energy from the power plant 3100 can be routed into the PHESsystem 3000.

In one embodiment, with the PHES system in charge mode, and the powerplant 3100 in a generation mode, heated fluid (e.g., hot air or steam)flowing in fluid path 3008 from power plant 3100 to preheater 3010 canbe used to preheat working fluid flowing to the compressor system 130,830, or 850 (acting as a compressor system). Preheater 3010 acts as aheat exchanger, transferring heat to the working fluid from the heatedfluid flowing into preheater 3010 from fluid path 3008, which isconnected to the power plant 3100. Preferably, preheater is in thermalcontact with the working fluid flowing through a low-pressuremedium-temperature fluid path (e.g., 908, 912, 917). The heated fluidmay be dumped to ambient or sent elsewhere after passing through thepreheater 3010. The working fluid, after passing through the preheater3010, is compressed in the turbine system (e.g., 130, 830, or 850(acting as a compressor system)) and continues through the working fluidloop (e.g., 300, 300C, or 300D).

Advantageously, the thermal integration with preheater embodiments canimprove the coefficient of performance in the PHES system 3000 becausethe charge compressor system must do less work. Additionally, if thetemperature of the heated fluid from the power plant 3100 issufficiently high, the charge compressor system can heat the hot HTSmedium 590 to a higher temperature than the non-integrated PHES 3000charge cycle alone. This can reduce or eliminate reliance on resistanceheating to raise the hot HTS medium 590 temperature. Alternatively, thepreheater embodiment can be used in conjunction with the resistiveheating as complementary means of achieving high temperature hot HTSmedium 590.

In another embodiment, with the PHES system 3000 in a charge mode or anidle mode, and the power plant 3100 in a generation mode, heat in theHTS tank 520 is provided to the power plant 3100, which may be a thermalplant. An HTS heat exchanger 3029 is provided to transfer heat from hotHTS medium 590 to the power plant 3100, for example to reheat steam inthe power plant 3100. This embodiment is discussed in greater detailbelow with respect to FIGS. 38 and 37A with the PHES system 3000 ingeneration mode, and the embodiment for the PHES system 3000 in chargemode operates in the same manner.

In another embodiment, with the PHES system 3000 in a charge mode or inan idle mode, and the power plant 3100 in a generation mode, the PHESsystem 3000 may supply cooling to the power plant 3100 (i.e., PHESsystem 3000 extracts heat from the power plant 3100). As illustrated inFIGS. 36 and 37B, the integrated system may include a fluid loop 3033that flows cold CTS medium 690 out of a cold CTS tank 620, through a CTSheat exchanger 3019, and returns warm CTS medium 690 to warm CTS tank610. Valve system 3031 may control the flow, including isolating CTSheat exchanger from the CTS medium 690. Pump 640 may circulate the CTSmedium 690, or alternatively or additional, one or more other pumps (notshown) within CTS system 691 or along fluid loop 3033 may circulate theCTS medium 690 through fluid loop 3033. A heated fluid (e.g., steam) maycirculate from the power plant 3100 through fluid path 3013, through CTSheat exchanger 3019 and in thermal contact with the cold CTS medium 690.The heated fluid transfer (i.e., dumps) heat to the cold CTS medium 690creating warm CTS medium 690, and the warm CTS medium 690 circulates tothe warm CTS tank 610. The formerly heated fluid is cooled (e.g.,condenses) and may returned to the power plant 3100 via fluid path 3015.Advantageously, in addition to providing cooling to the power plant3100, this embodiment can thermodynamically balance the thermal mass ofwarm CTS medium 690 in warm CTS tank 610 with warm HTS medium 590 in thewarm CTS tank 510.

C. PHES System Power Plant Thermal Integration—Generation Mode

FIG. 38 is a top-level schematic diagram of a PHES system 3000 ingeneration mode integrated with a power generation plant, according toan example embodiment. PHES system 3000 may be any PHES embodimentdescribed herein, including PHES systems 1000, 1003, 1005, 1200. FIG. 38illustrates that can each be separated from, or combined with, theresistive heating embodiment. As previously described, the PHES system3000 can be thermally integrated with the power plant 3100. If powerplant 3100 is a thermal power station, heat energy from the PHES system3000 in a generation mode can be routed into the power plant 3100 in ageneration mode. Additionally, heat can be routed out of the PHES system3000 and into the power plant 3100, which may occur, for example, whenthe PHES system is in a generation mode and the power plant 3100 is in ageneration mode.

FIG. 38A is a schematic diagram of a portion of powertrain system 3002thermally integrated with power plant 3100 via fluid path 3024,according to an example embodiment. In this embodiment, heat fromworking fluid flowing through a generation powertrain 3002 of PHESsystem 3000 in a generation mode can be used to preheat intake air forthe power plant 3100 in a generation mode.

Powertrain 3002 can be any PHES system powertrain disclosed herein forgeneration mode operation, including GPT system 200, SPT system 800 in ageneration mode configuration, and RPT system 801 in a generation modeconfiguration. For illustrative clarity, only select portions of thepowertrain system 3002 are illustrated. Illustrated are compressor inletinterconnects 26,31,36 and compressor outlet interconnects 22,28,35 forthe respective compressor systems 130, 830, or 852 (acting as acompressor), and turbine inlet interconnects 23,29,34 and turbine outletinterconnects 25,30,37 for the respective turbine systems 140, 840, or850 (acting as a turbine). The compressor system (e.g., 130, 830, 852)may include at least two stages, illustrated as compressor pairs130-1,130-2, or 830-1,830-2, or 852-1,852-2. Between the two stages, theworking fluid path may pass through a valve system 3028 which can directthe inter-stage working fluid to an intercooler 3026 or valve system3028 can bypass the intercooler 3026. As illustrated, working fluid inthe PHES system 3000 is compressed through the first compressor stage(e.g., 130-1) and then enters intercooler 3026. Intercooler 3026 acts asa heat exchanger, transferring heat from the working fluid to powerplant intake air (or another fluid) flowing through intercooler 3026.The working fluid, after passing through the intercooler 3026 and havingbeen cooled, is again compressed through the second compressor stage(e.g., 130-2) before exiting the compressor system (e.g., 130). Thepreheated intake air (or other fluid) then flows through fluid path 3024to power plant 3100. The preheated intake air (or other fluid) may beused in the power plant 3100 to improve efficiency of the plant byproviding heat energy to, for example, preheat water used in the thermalcycle of the power plant 3100. In an alternative embodiment, intake airor other fluid passing through the intercooler 3026 could originate inthe power plant 3100 and be used for other purposes. For example, thefluid could be a cool high-pressure condensate that arrives in a fluidpath (not illustrated) from the power plant 3100, is heated in theintercooler 3026, and is then returned to the power plant 3100 throughfluid path 3024.

Additional embodiments of the thermal integration with intercooler caninclude multiple intercoolers and multiple compressor stages.

Advantageously, the thermal integration with intercooler embodiments canprovide higher efficiency for the PHES system generation cycle, andtherefore higher round trip efficiency (i.e., charge plus generationcycle). Additionally, the power plant can experience higher generationefficiency as well. Finally, if sufficient heat is removed through theintercooler, the PHES system 3000 may be able to run with the AHX 700system bypassed or removed completely, thus further improving efficiencyand/or capital cost of the PHES system 3000.

Returning again to FIG. 38, additional embodiments are illustrated thatcan each be separated from, or combined with, resistive heatingembodiments and/or intercooler embodiments.

In one embodiment, with the PHES system 3000 in a generation mode andpower plant 3100 in a generation mode, ambient air (or another fluid)can be circulated through an active AHX system 700, where it is heated,and then it is directed through fluid path 3022 into power plant 3100.As previously described (e.g., with respect to FIG. 6B), AHX system 700can acts as a heat exchanger, preferably during operation of PHES system3000 in generation mode, and can transfer heat from the working fluid tothe ambient air (or another fluid). The preheated air can then be usedfor the same purposes in the power plant 3100, and with the sameefficiency advantages, as the preheated air in the intercoolerembodiments described with respect to FIG. 38A. Additionally, byreducing or eliminating exhaust heat dump from the PHES system 3000, theenvironmental impact of PHES system 3000 is improved. In alternativeembodiments, AHX system 700 may be run as part of a charge mode workingfluid loop to remove excess heat during charge mode operation of PHESsystem 3000. In those embodiments, heat can also be transferred via theAHX system 700 to the power plant 3100 while the PHES system 3000 is ina charge mode.

Referring to FIGS. 38 and 37A, another embodiment is provided where heatin the HTS tank 520 is provided to the power plant 3100, which may be athermal plant. This embodiment may be accomplished with the PHES system3000 in generation, idle, or charge mode. An HTS heat exchanger 3029 isprovided to transfer heat from hot HTS medium 590 to the power plant3100, for example to reheat steam in the power plant 3100.

An HTS heat exchanger 3029 can be positioned between hot HTS medium 590in hot HTS tank 520 and warm HTS medium 590 in warm HTS tank 510. An HTSmedium 590 fluid loop 3023 provides a circulation path between hot HTSmedium 590 in hot HTS tank 520 and warm HTS medium 590 in warm HTS tank510. A valve system 3021 can allow or isolate hot HTS medium 590 flowthrough the HTS heat exchanger 3029. In the illustrated embodiment ofFIG. 37A, pump 540 may be used to circulate the hot HTS medium 590 fromhot HTS tank 520, through the HTS heat exchanger 3029, and to the warmHTS tank 510; however, in alternative embodiments a separate pumpingsystem or gravity feed (not illustrated) may be used to circulate thehot HTS medium 590.

Fluid from the power plant 3100 in fluid path 3025 may be circulatedthrough the HTS heat exchanger 3029, and in thermal contact with the hotHTS medium from fluid loop 3023, such that heat is transferred from thehot HTS medium 590 to the fluid, and the now heated fluid is returned tothe power plant 3100. The heated fluid may be used in a reheater (e.g.,for reheating steam) in the power plant 3100.

In another embodiment, with the PHES system 3000 in a generation mode,and the power plant 3100 in a generation mode, the PHES system 3000 maysupply cooling to the power plant 3100 (i.e., PHES system 3000 extractsheat from the power plant 3100). As illustrated in FIGS. 38 and 37B, theCTS heat exchanger 3019 may extract heat from a power plant 3100 fluidflowing through fluid paths 3013, 3015. The extracted heat will betransferred to CTS medium 690. This embodiment is discussed in greaterdetail above with respect to FIGS. 36 and 37B with the PHES system 3000in charge or idle mode, and the embodiment for the PHES system 3000 ingeneration mode operates in the same manner.

D. PHES System Thermal Plant Integration with Steam Cycle

Power plant 3100 may be a steam plant 1800 or 1801. Such an integratedsteam plant and PHES system may include the thermal integration andelectrical integration features and operability previously describedwith respect to power plant 3100, as well as additional thermalintegration. For example, electric heater 3017 (see FIG. 38B) may beemployed as previously described to heat hot HTS medium 590.

Advantages of such integration include improving energy storage capacityand/or efficiency of energy storage. Additionally, such integration mayimprove performance of the steam plant operation (e.g. fuel consumption,lifetime, economics) by utilizing the thermal energy storage portion ofthe integration to meet power ramping requirements. Further, suchintegration could eliminate fuel consumption of the steam plant entirelyby replacing the fuel burning for the boiler with electricity chargingof thermal storage in the PHES system to feed the thermal requirementsof the steam plant, thereby converting an existing steam plant into anelectricity storage plant.

FIG. 42 is a top-level schematic diagram of a boiler-based steam plant1800 integrated with a PHES system 3000 in charge mode, according to anexample embodiment. FIG. 43 is a top-level schematic diagram of aboiler-based steam plant 1800 integrated with a PHES system 3000 ingeneration mode, according to an example embodiment. Steam plant 1800includes the thermal and electrical connections with the PHES system aspreviously described with respect to, e.g., FIGS. 36 through 38A.

As illustrated in FIGS. 38B, 42, 43, the integrated system may include afluid loop 3023 that flows hot HTS medium 590 out of a hot HTS tank 520and returns warm HTS medium 590 to warm HTS tank 510. Valve system 3021may control the flow. Pump 540 may circulate the HTS medium 590, oralternatively or additional, one or more other pumps (not shown) withinhot HTS tank 520 or along fluid loop 3023 may circulate the HTS medium590 through fluid loop 3023.

As illustrated in FIGS. 37B, 42, 43, the integrated system may include afluid loop 3033 that flows cold CTS medium 690 out of a cold CTS tank520 and returns warm CTS medium 690 to warm CTS tank 610. Valve system3031 may control the flow. Pump 640 may circulate the CTS medium 690, oralternatively or additional, one or more other pumps (not shown) withinCTS system 691 or along fluid loop 3033 may circulate the CTS medium 690through fluid loop 3033.

FIG. 44 is a top-level schematic diagram of steam plant 1800 integratedwith a PHES system 3000, according to an example embodiment. Steam plant1800 includes a boiler 1810. In power generation mode for the steamplant 1800, a burner 1811 combusts fuel with feed air 1812, creatingheated combustion gas 1819 that is circulated through the boiler 1810and eventually exits as hot flue gas 1813 (i.e., exhaust gas). Thecombustion gas 1819 transfers heat to a steam circulation system that isused to drive a steam turbine system 1827, which may include one or moreturbine stages 1820, 1821, that in turn drives a generator 1822,producing electrical power for distribution out of the integrated steamplant 800 and PHES system 1000. Turbine stages 1820, 1821 may be turbinestages within a single physical turbomachine or wholly separateturbines. Each of turbine stages 1820, 1821 may include multiplesequential stages or turbines and/or multiple parallel stages orturbines, or some combination thereof.

In one example flow path within the steam circulation system,high-pressure steam condensate may be circulated through a preheater1817 (e.g., an economizer) where the condensate is heated by thermalcontact with warm combustion gas 1819. The condensate may then travel toan evaporator 1814 where it begins to convert to steam through thermalcontact with hot combustion gas 1819. The steam may then be furtherheated in a superheater 1815 via thermal contact with hot combustion gas1819. From there, the high-pressure, high-temperature steam may exit theboiler 1810 and circulate through a turbine stage 1820, providingrotational torque to the generator 1822. A portion of the nowmedium-pressure, low-temperature steam exiting the turbine stage 1820may be fed back into the boiler 1810 and through a reheater 1816, wherethe steam temperature is increased through thermal contact with hotcombustion gas 1819. From there, the medium-pressure, nowhigh-temperature steam may again exit the boiler 1810 and feed a turbinestage 1821. A small portion of now low-pressure, low-temperature steammay exit the turbine stage 1821 and flow to a deaerator 1826 to aid inremoving dissolved gases in circulating condensate. A large portion ofthe now low-pressure, low-temperature steam may exit the turbine stage1821 and travel to a condenser 1823, where the steam is cooled and/orcondensed. Prior to the low-pressure, low-temperature steam reachingcondenser 1823, a bypass valve system 1841 may route the low-pressuresteam through a condenser heat exchanger (“CoHX”) system 1840 in thermalcontact with cold CTS medium 690 of the integrated PHES system 1000through fluid loop 3033, as illustrated, e.g., with reference to FIGS.37B, 42, 43. The condenser 1823 may use a water cooling tower 1824 tofurther aid cooling and/or condensation of the steam. One or more pumps1825 may then circulate the condensate into downstream fluid paths ofthe steam circulation system, including through the deaerator 1826. Apump 1828 may then pump the condensate up to high pressure, where fromthere at least a portion of the condensate may be circulated to thepreheater 1817 to complete the circulation cycle.

At least another portion of the high-pressure condensate from pump 1828may also circulate through a steam heat exchanger (“SHX”) system 1830that is in thermal contact with the PHES system 3000. The SHX system1830 may be similar to or the same as HTS heat exchanger 3029. In theexample embodiment illustrated in FIG. 44, the SHX system 1830 mayinclude a first flow path in which hot HTS medium 590 from hot HTS tank520 is thermally contacted with the condensate. Isolation valve system3021 (in FIG. 38B) may be opened to allow the hot HTS medium 590 tocirculate from hot HTS tank 520 through a proportioning valve 1837,through superheater 1832, through heater (e.g., an evaporator) 1833,through preheater 1834, and back through isolation valve system 3021into warm HTS tank 510. To provide heat transfer from the hot HTS medium590 into the steam plant 1800, high-pressure condensate from pump 1828may flow through preheater 1834, heater 1833 where the condensate may beconverted to steam, and through superheater 1832 where the steamincreases further in temperature. The high-pressure, high-temperaturesteam exiting the superheater 1832 in the SHX system 830 may combinewith the high-pressure, high-temperature steam exiting the superheater1815 in the boiler 810 and may be fed to the turbine stage 1820, whereit may be used to drive the generator 1822, producing electrical powerfor distribution out of the integrated steam plant 1800 and PHES system3000.

Alternatively or additionally, SHX system 1830 may include a second flowpath downstream from the proportioning valve 1837 in which hot HTSmedium 590 from hot HTS tank 520 may be thermally contacted with aportion of medium-pressure, low-temperature steam exiting turbine stage1820. Hot HTS medium 590 may circulated from hot HTS tank 520 throughproportioning valve 1837 and into reheater 1831, where the hot HTSmedium 590 may transfer heat to the steam from turbine stage 1820,increasing the temperature of the steam. Warm HTS medium 590 exiting thereheater 1831 may circulate back through isolation valve system 3021into warm HTS tank 510. Medium-pressure, high-temperature steam exitingreheater 1831 may combine with medium-pressure, high-temperature steamexiting reheater 1816 in the boiler 1810 and may be fed to turbine stage1821, which may be used to drive the generator 1822, producingelectrical power for distribution out of the integrated steam plant 1800and PHES system 3000.

In an alternative embodiment of steam plant 1800, FIG. 45 is a top-levelschematic diagram of steam plant 1801 integrated with a PHES system3000, according to an example embodiment. Steam plant 1801 may includethe thermal and electrical connections with the PHES system 3000 aspreviously described with respect to, e.g., FIGS. 36 through 38A, exceptPHES system 3000 might not use combustion exhaust heat from the steamplant, for example in fluid paths 3008 and 3012. Steam plant 1801 might,however, use heated fluid from other sources within steam plant 1801 influid paths 3008 and 3012. Steam plant 1801 may be substituted for steamplant 1800 in FIGS. 42 and 43. Steam plant 1801 is similar to steamplant 1800, except that it does not have a boiler 1810 and associatedfluid paths. Accordingly, the steam turbine system 1827 relies on heatstored in PHES system 3000 to generate electricity. High-pressurehigh-temperature steam from SHX system 1830, which can receive heatexclusively from the PHES system 3000 in accordance with the how steamplant 1800 operates, is circulated through the steam turbine system1827.

Modes of Operation

Integrated PHES system 3000 and steam plant 1800 (or 1801) includesthermal transfer between PHES system 1000 and steam plant 1800 (or1801). Thermal transfer may be accomplished through circulation of HTSmedium 590 and/or CTS medium 690 in thermal contact with steam and/orcondensate of steam plant 1800 (or 1801).

In one embodiment the PHES system 3000 in charge mode converts electricenergy into stored thermal energy in the HTS medium 590 and thermalenergy transfer with steam plant 800 may be blocked. To accomplish that,isolation valve system 3021 may prevent circulation of HTS medium 590out of the PHES system 2000 and into thermal contact with the steamand/or condensate, and isolation valve system 3031 may preventcirculation of CTS medium 690 out of the PHES system 3000 and intothermal contact with the steam and/or condensate. With PHES system 3000operating in charge mode, steam plant 1800 may operate in generationmode using heat from the burner 1811. Alternatively, with PHES system3000 operating in charge mode, steam plant 1800 (or 1801) maysimultaneously draw down hot HTS medium 590 that is being circulated bythe PHES system 3000 into the hot HTS tank 520.

During operation of the integrated steam plant 1800 and PHES system 3000in generation mode where the steam plant is producing electric power fordistribution, the PHES system 3000 may be idle. For example, PHES system3000 could be operating in slow-rolling, hot standby, or cold-drystandby modes previously described herein with respect to a standalonePHES system (e.g., 1000, 1003, 1005). During this time (or at othertimes), to prepare the PHES system 3000 for the next charge cycle, theCTS system 601 (see, e.g., FIG. 37B) may need to be rebalanced. In anexample embodiment, cold CTS medium 690 may be removed from cold CTStank 620, heated, and then added to warm CTS tank 610 as warm CTS medium690, thus restoring and/or improving the thermodynamic balance ofintegrated PHES system 100 in preparation for the next charge cycle. Inthis example embodiment, isolation valve system 3031 may be opened,allowing pump 640 (or another pump) to circulate cold CTS medium 690from cold CTS tank 620 through CoHX system 1840, which may include oneor more condensers where the cold CTS medium 690 may be thermallycontacted with low-pressure steam exiting the turbine stage 1821. Thelow-pressure steam may transfer heat to the CTS medium 690 and thelow-pressure steam may partially or fully condense before entering thecondenser 1823, where it is further condensed and/or cooled, therebyreducing the cooling load and water consumption of the water coolingtower 1824. Bypass valve system 1841 may be operated to directlow-pressure steam from turbine stage 1821 into CoHX system 1840 asneeded to transfer heat to the CTS medium 690. The bypass system 1841may direct none, some, or all of the low-pressure steam to the CoHXsystem 1840. For example, the bypass system 1841 is illustrated asdirecting all the low-pressure steam to the CoHX system 1840; however,the bypass system 1841 may partially open a valve on the fluid pathbetween turbine stage 1821 and condenser 1821, thus allowing somelow-pressure steam to bypass the CoHX system 1841 and directly flow tocondenser 1823. Warm CTS medium 690 may exit the CoHX system 1840 andflow back through isolation valve system 3033 and into warm CTS tank610. When the CTS medium 690 is at an appropriate thermal mass in thewarm CTS tank 610 to thermodynamically balance the thermal mass of warmHTS medium 590 in the warm CTS tank 510, the PHES system 3000 may beconsidered rebalanced and available to operate in charge mode again.

In a related embodiment, isolation valve system 3031 may be opened,allowing pump 640 (or another pump) to circulate cold CTS medium 690from cold CTS tank 620 to one or more alternate cooling loads (notillustrated), such as building cooling, HVAC systems, or industrialrefrigeration. Heat from those cooling loads could warm the CTS medium690, which could return from the alternate cooling load throughisolation valve system 3031 to warm CTS tank 610.

In one embodiment, the integrated PHES system 3000 and steam plant 1800(or 1801) produce electrical power for distribution solely through thesteam plant generator 1822. Thus, the PHES system 3000 need not operatein generation mode. Consequently, the PHES system 3000 can forgo thegeneration powertrains (e.g., GPT powertrain 200) of a standalone PHESsystem 3000, including associated PHES generation-only flow-paths, valvesystems, and optionally AHX 700, thus simplifying the overallarrangement of PHES system 3000 when integrated with steam plant 1800(or 1801) in this embodiment. In effect, PHES system 3000 operatessolely as a heat pump and not also as a heat engine. This has theadvantage of significantly reducing cost and operational complexity ofthe PHES system.

In another embodiment, integrated PHES system 3000 may operate ingeneration mode integrated simultaneously with steam plant 1800 (or1801) operating in generation mode. Integrated PHES system 3000 ingeneration mode can generate electrical power for distribution outsideof the PHES system 3000, for example to an electrical grid, a localload, and/or for consumption within the integrated PHES system 3000 andsteam plant 1800 (or 1801).

In this parallel generation mode of the integrated PHES system 1000 andsteam plant 1800 (or 1801), valve systems 3021 and 3031 may be open,allowing thermal contact between the HTS medium 590 and the SHX system1830, and optionally between the CTS medium 690 and the CoHX system 840,as previously described.

XII. Cogeneration System and Control

FIG. 39 is a schematic diagram of cogeneration system 1220, which mayinclude cogeneration control of the PHES system 3000 integrated with thepower plant 3100, according to an example embodiment.

In this configuration, the power plant 3100 may supply a portion of itselectrical output to the PHES system 3000. This may be done when thepower plant 3100 is required to reduce its output (e.g., based on adirective from a grid operator, via, e.g., a grid dispatch controller3400) to maintain grid stability. The PHES system 3000 may be sized(e.g., megawatt capacity) such that it can accept some or all of theelectricity that the power plant 3100 cannot send to the grid (if thepower plant 3100 was running at 100%). Alternatively, the PHES system3000 may be sized such that it can accept the minimum output power ofthe power plant 3100, allowing the power plant to remain operating evenwhen grid demand is zero, thus avoiding frequent power plant shutdownand associated startup costs. The PHES system 3000 can then laterdischarge energy to the grid when there is higher demand forelectricity.

A cogeneration dispatch controller 3300 may receive directives from agrid operator, optionally through a grid dispatch controller 3400. Thegrid dispatch controller 3400 may instruct the cogeneration dispatchcontroller 3300 to increase or decrease power supplied to the gridand/or load consumed from the grid. Alternatively or additionally, thegrid dispatch controller 3400 may issue instructions to the power plant3100, which may pass the instructions and/or responsively provideinstructions and/or data to the cogeneration dispatch controller 3300over a signal path 3042. Alternative or additionally, the power plant3100 may issue instructions or data to the cogeneration dispatchcontroller 3300 based on other data.

The cogeneration dispatch controller 3300 may communicate with, and/ordirect, the PHES system 3000. The cogeneration dispatch controller mayreceive state and/or mode information from the PHES system 3000,including power level (charge or generation), state of charge, systemavailability, etc. The cogeneration dispatch controller 3300 may directthe PHES system, including to change power levels and/or operation mode(e.g., from charge to generation or vice-versa. This may be done basedon data received at the cogeneration dispatch controller 3300 orresponsively to instructions received at the cogeneration dispatchcontroller 3300.

From sensor 3004S, the cogeneration dispatch controller 3300 may receivedata regarding power traveling to/from the PHES system 3000, and/or fromsensor 3003S, the cogeneration dispatch controller 3300 may receive dataregarding power traveling from the power plant 3100. Such data mayinclude, for example, voltage, amperage, and/or frequency.

Advantageously, the power plant 3100 can optionally maintain 100% ratedoutput power at all time (at least until the PHES system 3000 reachesfull charge capacity), keeping the power plant's at high efficiency andoverall low emission. Additionally, the charged PHES system 3000, whichmay have been charged using inexpensive excess electricity, can sellelectricity to the grid at a high margin. Further, this cogenerationintegration can effectively increase the total capacity of theintegrated system (power of the power plant 3100 plus power of PHESsystem 3000). Also, power plant 3100 and PHES system 3000 can beoperated independently, as desired.

FIG. 40 is a simplified block diagram illustrating components of acogeneration system 1220, according to an example embodiment.

The cogeneration system 1220 may include one or more sensors 1224, acommunication system 1228, a controller system 1236, one or moreprocessors 1230, and a data storage 1232 on which program instructions1234 may be stored. The cogeneration system 1220 may further include aPHES system 3000. The PHES system 3000 may take the form of, or besimilar in form, to any PHES system herein, including PHES system 1000,1003, 1005, 1200. The cogeneration system 1220 includes a power plant3100 and may optionally include a thermal load 3200. The components ofcogeneration system 1220 may communicate, direct, and/or be directed,over one or more communication connections 1222 (e.g., a bus, network,PCB, etc.). T

The sensors 1224 may include a range of sensors, including monitoringand reporting devices that can provide operating conditions in thecogeneration system 1220, including one or more of pressure,temperature, flow rate, dewpoint, turbomachinery speed, fan speed, pumpspeed, valve state, mass flow rate, switch state, voltage, amperage,frequency, power, fluid level, and/or fluid concentration data, to oneor more control systems and/or controllers controlling and/or monitoringconditions of a PHES system. Sensors 1224 may include monitoring andreporting devices that can provide operating conditions in and betweencomponents of the cogeneration system 1220, including PHES system 3000,power plant 3100, thermal load 3200, and operating conditions of fluidor electrical paths between and among the components of the cogenerationsystem. Sensors 1224 may further include monitoring and reportingdevices that provide operating conditions of components outside thecogeneration system 1220. For example, sensors 1224 may monitor andreport operating frequency of the electrical grid.

The control system 1236 can function to regulate and/or control theoperation of the PHES system 3000 in accordance with instructions and/ordata from the PHES system 3000, another entity, control system, and/orbased on information output from the sensors 1224. The control systemincludes a cogeneration dispatch controller 3300. In some embodiments,the control system may optionally include one or both of the PHESSupervisory Controller 1124 and/or the ICS Controller 1125. The controlsystem 1236 may therefore be configured to direct operation of the PHESsystem 3000, for example by directly controlling the PHES system 3000and/or sending instructions and/or signals to PHES SupervisoryController 1124, The control system 1236 may further be configured tooperate various valves, switches/breakers, fans, and/or pumps thataffect interaction of the PHES system 3000 with the power plant 3100and/or thermal load 3200. The control system 1216 may be implemented bycomponents in whole or in part in the cogeneration system 1220 and/or byremotely located components in communication with the cogenerationsystem 1220, such as components located at stations that communicate viathe communication system 1228. The control system 1236 may beimplemented by mechanical systems and/or with hardware, firmware, and/orsoftware. As one example, the control system 1236 may take the form ofprogram instructions 1234 stored on a non-transitory computer readablemedium (e.g., the data storage 1232) and a processor (or processors)1230 that executes the instructions. The control system 1236 may includethe cogeneration dispatch controller 3300, as well as other controllers.

The cogeneration system 1220 may include a communication system 1228.The communications system 1228 may include one or more wirelessinterfaces and/or one or more wireline interfaces, which allow thecogeneration system 1220 to communicate via one or more networks. Suchwireless interfaces may provide for communication under one or morewireless communication protocols. Such wireline interfaces may includean Ethernet interface, a Universal Serial Bus (USB) interface, orsimilar interface to communicate via a wire, a twisted pair of wires, acoaxial cable, an optical link, a fiber-optic link, or other physicalconnection to a wireline network. The cogeneration system 1220 maycommunicate within the cogeneration system 1220, with other stations orplants, and/or other entities (e.g., a command center) via thecommunication system 1228. The communication system 1228 may allow forboth short-range communication and long-range communication. Thecogeneration system 1220 may communicate via the communication system1228 in accordance with various wireless and/or wired communicationprotocols and/or interfaces.

The cogeneration system 1220 may include one or more processors 1230,data storage 1232, and program instructions 1234. The processor(s) 1230may include general-purpose processors and/or special purpose processors(e.g., digital signal processors, application specific integratedcircuits, etc.). The processor(s) 1230 can be configured to executecomputer-readable program instructions 1234 that are stored in the datastorage 1232. Execution of the program instructions can cause thecogeneration system 1220 to provide at least some of the functionsdescribed herein.

One or more controllers may be used to control cogeneration system 1220.A cogeneration dispatch controller 3300 may determine and/or directcogeneration system 1220 actions, including directing the PHES system3000 to change modes or power levels, and/or to determine and/or directpower transfer between or among PHES system 3000, the power plant 3100,and/or an electrical grid, and/or to determine and/or direct heattransfer between or among PHES system 3000, the power plant 3100, and/ora thermal load 3200. Alternatively or additionally, the cogenerationdispatch controller 3300 may receive directives and/or data from thePHES system 3000, the power plant 3100, the thermal load 3200, and/or agrid dispatch controller 3400, and responsively enact changes in PHESsystem 3000 (e.g., change power level), power plant 3100 (e.g., changepower level) and/or cogeneration system 1200, and/or report conditionsto PHES supervisory controller 1124 or to power plant 3100. For example,a dispatch signal originating with the grid controller 3400 can bereceived by the cogeneration dispatch controller 3300, and thecontroller 3300 can responsively direct the PHES supervisory controller1124 to start/increase generation power or start/increase charge load,respectively. Additionally or alternatively, the cogeneration dispatchcontroller 3300 could direct the power plant 3100 to increase ordecrease power generation.

Cogeneration dispatch controller 3300 may monitor pressure, temperature,and/or flowrate of steam or other fluid moving between one or more ofthe PHES system 3000, power plant 3100, and/or thermal load 3200.Cogeneration dispatch controller 3300 may monitor electric power flowingbetween one or more of PHES system 3000, power plant 3100, and/or theelectrical grid.

XIII. District Heating

A PHES system 3000 integrated with a power plant 3100 may be capable ofsupplying waste heat from the PHES system 3000 to a thermal load. In oneembodiment, the thermal load 3200 may be a district heating systemproviding residential and/or commercial heating. FIG. 41 is a schematicdiagram of district heating with an integrated PHES system 3000,according to an example embodiment.

In a district heating system, a power plant 3100 that operates as athermal plant may supply heat (e.g., steam) to a thermal load 3200, suchas one or more office buildings, educational institutions, or healthcare facilities. Heat may be supplied to the thermal load 3200 as afluid (e.g., hot steam) via a fluid path 3030 and cooled fluid (e.g.,cold steam or condensed steam) may be returned to the power plant 3100for reheating.

PHES system 3000 may generate excess heat, which needs to be removedfrom the system. Preferably, excess heat may be dumped during generationmode, and it may be dumped via the AHX system 700 as described elsewhereherein. A fluid path 3034 may connect to cooled fluid path 3032 anddirect some or all of the cooled fluid into the AHX system 700 atinterconnect 29 of the PHES system 3000. Fluid flow in fluid path 3034may be assisted with a fan 3037 (or a pump if in liquid phase). Withinthe AHX system 700, the cooled fluid is thermally contacted with the hotworking fluid in the working fluid loop and consequently heated beforebeing returned via fluid path 3036 to the supply fluid path 3030 for useat the thermal load 3200.

Advantageously, this provides a cost return for otherwise excess heatand provides an environmental benefit by reducing or eliminating wasteheat dump to the ambient environment.

We claim:
 1. A method comprising: operating a pumped heat energy storage(“PHES”) system in a charge mode to convert electrical energy intostored thermal energy in a hot thermal storage medium (“HTS medium”),wherein operating the PHES system in the charge mode comprises:circulating a working fluid through, in sequence, at least, a firstcompressor, a hot-side heat exchanger, a first turbine, and a cold-sideheat exchanger, in the hot-side heat exchanger, transferring heat fromthe working fluid to the HTS medium; flowing a hot HTS medium from thePHES system to a thermal power plant; and receiving at the PHES system awarm HTS medium from the thermal power plant, wherein the hot HTS mediumhas discharged heat to the thermal power plant.
 2. The method of claim1, wherein flowing the hot HTS medium from the PHES system to thethermal power plant comprises flowing the hot HTS medium from a hot HTStank in the PHES system to the thermal power plant.
 3. The method ofclaim 1, further comprising: flowing a cold thermal storage medium (“CTSmedium”) from the PHES system to the thermal power plant; and receivingat the PHES system a warm CTS medium from the thermal power plant,wherein the cold CTS medium has received heat from the thermal powerplant, wherein operating the PHES system in the charge mode furthercomprises: in the cold-side heat exchanger, transferring heat from thewarm CTS medium to the working fluid.
 4. The method of claim 3, whereinflowing the cold CTS medium from the PHES system to a thermal powerplant comprises flowing the cold CTS medium from a cold CTS tank in thePHES system to the thermal power plant.
 5. The method of claim 1,wherein flowing the hot HTS medium from the PHES system to the thermalpower plant comprises flowing the hot HTS medium from the PHES system tothe thermal power plant while the PHES system is operating in the chargemode.
 6. The method of claim 1, wherein flowing the hot HTS medium fromthe PHES system to the thermal power plant comprises flowing the hot HTSmedium from the PHES system to the thermal power plant while the PHESsystem is not operating in the charge mode.
 7. The method of claim 1,wherein at least some of the electrical energy is received at the PHESsystem from the thermal power plant.
 8. The method of claim 1, furthercomprising: subsequent to operating the PHES system in the charge mode,operating the PHES system in a generation mode to convert the storedthermal energy into new electrical energy.
 9. A method comprising: at athermal power plant, receiving a hot thermal storage medium (“HTSmedium”) from a pumped heat energy storage (“PHES”) system; dischargingheat from the received hot HTS medium at the thermal plant; and flowinga warm HTS medium from the thermal power plant to the PHES system,wherein the hot HTS medium received heat at the PHES system in ahot-side heat exchanger from a working fluid that circulated through, insequence, at least, a first compressor, the hot-side heat exchanger, afirst turbine, and a cold-side heat exchanger.
 10. The method of claim9, wherein receiving the hot HTS medium from the PHES system comprisesreceiving the hot HTS medium from a hot HTS tank.
 11. The method ofclaim 11, further comprising: at the thermal power plant, receiving acold thermal storage medium (“CTS medium”) from the PHES system;discharging heat from the thermal power plant to the cold CTS medium;and flowing a warm CTS medium from the thermal power plant to the PHESsystem,
 12. The method of claim 11, wherein receiving the cold CTSmedium from the PHES system comprises receiving the cold CTS medium froma cold CTS tank.
 13. The method of claim 11, wherein receiving the hotHTS medium from the PHES system comprises receiving the hot HTS mediumfrom the PHES system while the PHES system is operating in a chargemode.
 14. The method of claim 11, wherein receiving the hot HTS mediumfrom the PHES system comprises receiving the hot HTS medium from thePHES system while the PHES system is not operating in a charge mode. 15.The method of claim 11, further comprising supplying electrical energyfrom the thermal power plant to the PHES system.